SMU - Revised Steering Wheel and Column Diagnostics
| Subject: | Revised Steering Wheel and Column Diagnostics |
| Models: | 2003-2004 Chevrolet Corvette |
This bulletin is being issued to revise various diagnostic procedures in the Steering Wheel and Column sub-section of the Service Manual. Please replace the current information in the Service Manual with the following information.
The following information has been updated within SI. If you are using a paper version of this Service Manual, please make a reference to this bulletin on the affected page.
Diagnostic System Check - Steering Wheel and Column
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
-
Determine if any Seat Control Module, Body Control Module, or Powertrain Control Module DTCs are present.
-
The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.
Step | Action | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|
1 | Install a scan tool. Does the scan tool power up? | Go to Step 2 | Go to Scan Tool Does Not Power Up in Data Link Communications | ||||||
Does the scan tool communicate with these systems? | Go to Step 3 | Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications | |||||||
Does the scan tool display any DTCs? | Go to Step 4 | Go to Symptoms - Steering Wheel and Column | |||||||
Does the scan tool display any DTCs which begin with a "U"? | Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications | Go to Step 5 | |||||||
5 | Does the scan tool display DTC B0605? | Go to DTC B0605 in Body Control Systems | Go to Step 6 | ||||||
6 | Does the scan tool display DTC P0562 or P0563? | Go to Diagnostic System Check - Automatic Transmission in Automatic Transmission | Go to Diagnostic Trouble Code (DTC) List |
DTC B2587
Circuit Description
The Body Control Module (BCM) provides the steering column control function which allows the column to be electronically locked or unlocked. The BCM provides three outputs, steering column lock, steering column unlock, and a steering column lock relay control. The BCM can apply a ground or battery output on the steering column lock or steering column unlock depending on the desired steering column lock motor position. The BCM uses the feedback switch in order to monitor the motor position and determine if the commanded position was accomplished.
The BCM controls the position of the steering column lock motor based on the following input information:
| • | Ignition position |
| • | Key IN ignition status |
| • | Key OUT of Ignition status |
| • | Steering column lock feedback switch |
| • | PASS-Key® system |
| • | PCM password information |
| • | System voltage |
The BCM also monitors its circuitry for the steering column lock circuit. If the BCM detects a malfunction present a DTC will set.
Conditions for Setting the DTC
| • | The BCM detects an internal malfunction, an open or a short to ground, in the column lock drive A circuit. |
| • | There is an open in the BCM battery positive voltage circuit from BCM2 fuse. |
| • | The condition must be present for 100 ms. |
Action Taken When the DTC Sets
| • | Stores a DTC B2587 in the BCM memory. |
| • | The PCM may disable fuel if vehicle speed is detected over 2.4 km/h (1.5 mph). |
| • | Sends a message to the IPC to display the SERVICE COLUMN LOCK message. |
Conditions for Clearing the DTC
| • | The BCM no longer detects an internal malfunction, an open or a short to ground, in the steering column lock circuit. |
| • | Supply voltage is available on the battery positive voltage circuit from BCM2 fuse. |
| • | A history DTC will clear after 50 consecutive ignition cycles if the condition for the malfunction is no longer present. |
| • | Use a scan tool. |
Diagnostic Aids
| • | The following conditions may cause an intermittent malfunction: |
| - | There is an intermittent open in BCM battery positive voltage circuit from BCM2 fuse. |
| - | The steering column lock or unlock circuits are shorted together or to ground. |
| • | A short to ground in the BCM battery positive voltage circuit will cause BCM2 fuse to open. The BCM receives supply voltage for the steering column lock motor through the BCM battery positive voltage circuit. If the BCM is unable to supply voltage to the steering column lock motor through the BCM battery positive voltage circuit, the BCM will set a DTC B2587. |
| • | Disconnecting or opening the steering column lock feedback circuit with the ignition in the ON position will cause the BCM to enter a Fail Enable Standby mode. The steering column will remain inoperative until the Fail Enable Standby mode is cleared. To clear this mode, disconnect the BCM1 & IPC fuse in the I/P fuse block for 15 seconds. |
| • | The BCM1 fuse will become open if the steering column lock motor or the steering column lock or unlock circuits are shorted together or to ground. |
| • | If the DTC is a history DTC, the problem may be intermittent. Perform the tests shown while moving related wiring and connectors. This can often cause the malfunction to occur. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Tests for an open in the BCM2 fuse. BCM2 fuse supplies power to the BCM to operate the steering column lock motor.
-
Tests for an open in the BCM battery positive voltage circuit at the BCM.
-
Tests for an open or short to ground in the BCM battery positive voltage circuit between the steering column lock relay and the I/P fuse block.
-
Tests for an open or short to ground in the steering column lock or unlock circuit. If steering column lock or unlock circuit is shorted to ground the BCM2 fuse will open.
-
When the BCM is replaced, use a scan tool to perform the BCM RPO Reprogram procedure.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Column/Ignition Lock Schematics Connector End View Reference: Steering Wheel and Column Connector End View | |||
1 | Did you perform the Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System - Steering Wheel and Column |
Test BCM2 fuse for an open. Did you find the fuse open? | Go to Step 4 | Go to Step 3 | |
Does the test lamp illuminate? | Go to Step 6 | Go to Step 4 | |
Test the BCM battery positive voltage circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 5 | |
Test the steering column lock and unlock circuits for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 7 | |
6 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 8 |
7 | Replace the steering column lock motor. Refer to Steering Wheel Theft Deterrent Lock Replacement in Steering Wheel and Column. Did you complete the replacement? | Go to Step 9 | -- |
|
Important: Perform the BCM RPO Reprogram procedure. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System. Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the replacement? | Go to Step 9 | -- | |
9 |
Does the DTC reset? | Go to Step 2 | System OK |
DTC B2592
Circuit Description
The BCM provides the steering column control function which allows the column to be electronically locked or unlocked. The BCM provides three outputs, steering column lock, steering column unlock, and a steering column lock relay control. The BCM can apply a ground or battery output on the steering column lock or steering column unlock depending on the desired steering column lock motor position. The BCM uses the feedback switch in order to monitor the motor position and determine if the commanded position was accomplished.
The BCM controls the position of the steering column lock motor based on the following input information:
| • | Ignition position |
| • | Key IN ignition status |
| • | Key OUT of ignition status |
| • | Steering column lock feedback switch |
| • | PASS-Key® system |
| • | PCM password information |
| • | System voltage |
The BCM also monitors its circuitry for the steering column unlock circuit. If the BCM detects a malfunction present a DTC will set.
Conditions for Setting the DTC
| • | The BCM detects an internal malfunction, an open or a short to ground, in the steering column unlock circuit. |
| • | There is an open in the BCM battery positive voltage circuit from BCM2 fuse. |
| • | The condition must be present for 100 ms. |
Action Taken When the DTC Sets
| • | Stores a DTC B2592 in the BCM memory. |
| • | The PCM may disable fuel if vehicle speed is detected over 2.4 km/h (1.5 mph). |
| • | Sends a message to the IPC to display the SERVICE COLUMN LOCK message. |
Conditions for Clearing the DTC
| • | The BCM no longer detects an internal malfunction, an open or a short to ground, in the column unlock circuit. |
| • | Supply voltage is available on the battery positive voltage circuit from BCM2 fuse. |
| • | A history DTC will clear after 50 consecutive ignition cycles if the condition for the malfunction is no longer present. |
| • | Use a scan tool. |
Diagnostic Aids
| • | The following conditions may cause an intermittent malfunction: |
| - | There is an intermittent open in BCM battery positive voltage circuit from BCM2 fuse. |
| - | The steering column lock or unlock are shorted together or to ground. |
| • | A short to ground in the BCM battery positive voltage circuit will cause BCM2 fuse to open. The BCM receives supply voltage for the steering column lock motor through the BCM battery positive voltage circuit. If the BCM is unable to supply voltage to the steering column lock motor through the BCM battery positive voltage circuit, the BCM will set a DTC B2592. |
| • | Disconnecting or opening the steering column lock feedback circuit with the ignition in the ON position will cause the BCM to enter a Fail Enable Standby mode. The steering column will remain inoperative until the Fail Enable Standby mode is cleared. To clear this mode, disconnect the BCM1 & IPC fuse in the I/P fuse block for 15 seconds. |
| • | The BCM2 fuse will become open if the steering column lock motor or the steering column lock or unlock circuits are shorted together or to ground. |
| • | If the DTC is a history DTC, the problem may be intermittent. Perform the tests shown while moving related wiring and connectors. This can often cause the malfunction to occur. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Tests for an open in the BCM2 fuse. BCM2 fuse supplies power to the BCM to operate the steering column lock motor.
-
Tests for an open in the BCM battery positive voltage circuit at the BCM.
-
Tests for an open or short to ground in the BCM battery positive voltage circuit at the steering column lock relay.
-
Tests for an open or short to ground in the steering column lock or unlock circuit. If steering column lock or unlock circuit is shorted to ground the BCM2 fuse will open.
-
When the BCM is replaced, use a scan tool to perform the BCM RPO Reprogram procedure.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Column/Ignition Lock Schematics Connector End View Reference: Steering Wheel and Column Connector End Views | |||
1 | Did you perform the Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Steering Wheel and Column |
Test BCM2 fuse for an open. Did you find the fuse open? | Go to Step 4 | Go to Step 3 | |
Does the test lamp illuminate? | Go to Step 6 | Go to Step 4 | |
Test the BCM battery positive voltage circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 5 | |
Test the steering column lock and unlock circuits for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 7 | |
6 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 8 |
7 | Replace the steering column lock motor. Refer to Steering Wheel Theft Deterrent Lock Replacement. Did you complete the replacement? | Go to Step 9 | -- |
|
Important: Perform the BCM RPO Reprogram procedure. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System. Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the replacement? | Go to Step 9 | -- | |
9 |
Does the DTC reset? | Go to Step 2 | System OK |
Electronic Column Lock Does Not Unlock
Diagnostic Aids
| • | An open on the key in ignition switch signal circuit will intermittently cause the column not to unlock. |
| • | Disconnecting or opening the steering column lock feedback circuit will cause the BCM to enter a Fail Enable Standby mode. The steering column will remain inoperative until the Fail Enable Standby mode is cleared. To clear this mode, disconnect the BCM1 & IPC fuse in the I/P fuse block for 15 seconds. |
Test Description
The number below refers to the step number on the diagnostic table.
-
This test can be performed with ignition ON or ignition OFF. This test confirms that the BCM is providing power to the steering column lock circuit.
-
This test can be performed with ignition ON or ignition OFF. This test confirms that the BCM is providing ground to the steering column unlock circuit.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Column/Ignition Lock Schematics Connector End View Reference: Steering Wheel and Column Connector End Views | |||
1 | Did you perform the Steering Wheel and Column Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Steering Wheel and Column |
2 | Verify the fault is present. Does the system operate normally? | Go to Diagnostic Aids | Go to Step 3 |
With a test lamp, back probe between steering column lock circuit on the BCM and ground. Does the test lamp illuminate? | Go to Step 4 | Go to Step 8 | |
With a test lamp, back probe between steering column unlock circuit on the BCM and battery voltage. Does the test lamp illuminate? | Go to Step 5 | Go to Step 8 | |
5 | Test the steering column lock and unlock circuits for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 6 |
6 | Test the steering column lock relay control circuit for an open or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 7 |
7 | Inspect for poor connections at the harness connector of the steering column lock. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 9 |
8 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 10 |
9 | Replace the steering column lock. Refer to Steering Wheel Theft Deterrent Lock Replacement in Steering Wheel and Column. Did you complete the replacement? | Go to Step 11 | -- |
10 |
Important: Perform the BCM RPO Reprogram procedure. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System. Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the replacement? | Go to Step 11 | -- |
11 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
Electronic Column Lock Does Not Lock
Diagnostic Aids
| • | An open on the key in ignition switch signal circuit will intermittently cause the column not to unlock. |
| • | Disconnecting or opening the steering column lock feedback circuit will cause the BCM to enter a Fail Enable Standby mode. The steering column will remain inoperative until the Fail Enable Standby mode is cleared. To clear this mode, disconnect the BCM1 & IPC fuse in the I/P fuse block for 15 seconds. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Column/Ignition Lock Schematics Connector End View Reference: Steering Wheel and Column Connector End Views | |||
1 | Did you perform the Steering Wheel and Column Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Steering Wheel and Column |
2 | Verify the fault is present. Does the system operate normally? | Go to Diagnostic Aids | Go to Step 3 |
3 |
Does the test lamp illuminate momentarily? | Go to Step 4 | Go to Step 7 |
4 |
Does the test lamp illuminate momentarily? | Go to Step 5 | Go to Step 7 |
5 | Test the steering column lock and unlock circuits for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 6 |
6 | Test the steering column lock relay control circuit for an open or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 10 |
7 | Test the key out of ignition switch signal and key in ignition switch signal circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 8 |
8 | Test the steering column lock relay control circuit for an open or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 9 |
9 | Test the ignition switch ground circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 11 |
10 | Inspect for poor connections at the harness connector of the steering column lock. Refer to Testing for Intermittent and Poor Connection and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 12 |
11 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 13 |
12 | Replace the steering column lock. Refer to Steering Wheel Theft Deterrent Lock Replacement in Steering Wheel and Column. Did you complete the replacement? | Go to Step 14 | -- |
13 |
Important: Perform the BCM RPO Reprogram procedure. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System. Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the replacement? | Go to Step 14 | -- |
14 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
Service Column Lock Indicator Always On
Diagnostic Aids
| • | An open on the key in ignition switch signal circuit will intermittently cause the column not to unlock. |
| • | Disconnecting or opening the steering column lock feedback circuit will cause the BCM to enter a Fail Enable Standby mode. The steering column will remain inoperative until the Fail Enable Standby mode is cleared. To clear this mode, disconnect the BCM1 & IPC fuse in the I/P fuse block for 15 seconds. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Column/Ignition Lock Schematics Connector End View Reference: Steering Wheel and Column Connector End Views | |||
1 | Did you perform the Steering Wheel and Column Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Steering Wheel and Column |
2 | Verify the fault is present. Does the system operate normally? | Go to Diagnostic Aids | Go to Step 3 |
3 | Verify that the column will lock or unlock cycling the steering column lock function by cycling the ignition key and also removing the ignition key. Does the steering column lock unlock and lock normally? | Go to Step 4 | Go to Electronic Column Lock Does Not Unlock or Electronic Column Does Not Lock |
4 | With a test lamp, back probe between steering column lock signal circuit on the BCM and a good ground. Does the test lamp illuminate? | Go to Step 5 | Go to Step 7 |
5 | Test the control and ground circuit of the steering column lock feedback switch for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 6 |
6 | Inspect for poor connections at the harness connector of the steering column lock. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 8 |
7 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 9 |
8 | Replace the steering column lock. Refer to Steering Wheel Theft Deterrent Lock Replacement in Steering Wheel and Column. Did you complete the replacement? | Go to Step 10 | -- |
9 |
Important: Perform the BCM RPO Reprogram procedure. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System. Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the replacement? | Go to Step 10 | -- |
10 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
Battery Electrical Drain/Parasitic Load Test
Tools Required
J 38758 Parasitic Draw Test Switch
Diagnostic Aids
| • | Be sure to rule out any possible obvious influences, such as customer error or aftermarket equipment. |
| • | Customer driving habits, such as regular short trips. This does not allow enough time to properly charge the battery. Refer to Battery Description and Operation. |
| • | Verify that the battery and charging system are in proper working order. Refer to Battery Charging and Charging System Test. |
| • | A battery discharging for no apparent reason while the vehicle is parked can be caused by an intermittent draw, such as a module waking up, or a continuous draw, such as a dome light or stuck relay. |
| • | Some systems and modules such as OnStar®, and regulated voltage control (RVC), if equipped, are designed to wake-up, perform a task, and go back asleep at regular intervals. Refer to Body Control System Description and Operation in Body Control System for the system or modules description and operation. |
| • | Remote keyless entry (RKE) will wake up due to an outside input. Refer to Keyless Entry System Description and Operation in Keyless Entry. |
| Important: The battery specification listed below is a generic specification. Refer to Battery Usage when testing the battery. |
| • | The battery run down time will vary depending on cold cranking amperage (CCA) and reserve capacity (RC). If the CCA and RC are higher, then the battery run down time would be longer. If the CCA and RC are lower, then the battery run down time would be shorter. The graph below indicates roughly how many days a 690 CCA battery with at 110 min. RC (60.5 AH) starting at 80 percent state of charge will last with a constant current draw until it reaches 50 percent state of charge. Differences in battery rating and temperature will affect the results. |
Current Drain | Days |
|---|---|
25 mA | 30.5 |
50 mA | 16.5 |
75 mA | 11 |
100 mA | 8.25 |
250 mA | 3.3 |
500 mA | 1.65 |
750 mA | 1 |
1 A | 0.8 |
2 A | 0.4 |
Caution: Refer to Battery Disconnect Caution in Cautions and Notices.
Notice: Do not turn the parasitic draw test switch to the OFF position with the engine running. Damage will occur to the vehicle's electrical system.
Notice: The test switch must be in the ON position when removing the fuses in order to maintain continuity in the electrical system. This avoids damaging the digital multimeter due to accidental overloading, such as a door being opened to change a fuse.
Important: The switch knob (1) on the J 38758 is marked ON and OFF. When the switch knob is in the ON position, the circuit is closed and electrical current will pass through the switch. When the switch knob is in the OFF position, the circuit is open and electrical current will not pass through the switch.
- Disconnect the battery negative cable from the battery negative terminal.
- Install the male end of the J 38758 to the battery ground terminal.
- Turn the J 38758 knob to the OFF position.
- Install the battery negative cable to the female end of the J 38758.
- Turn the J 38758 knob to the ON position.
- Road test the vehicle and activate ALL of the accessories, including the radio and air conditioning. This may take up to 30 minutes.
- Park the vehicle. Turn the ignition switch to the OFF position and remove the ignition switch key.
- Connect a 10A fused jumper wire to the test switch tool terminals.
- Turn the J 38758 knob to the OFF position. The current now flows through the jumper wire.
- Wait 1 minute. If the fuse blows, install an inductive ammeter and go to step 20.
- Remove the fused jumper wire.
- Set a digital multimeter to the 10A scale.
- Connect the digital multimeter to the test switch tool terminals.
- Turn the J 38758 knob to the OFF position. The current flows now through the digital multimeter.
- Wait 1 minute. Check and record the current reading.
- Turn the J 38758 knob to the OFF position. Wait 15 minutes for most vehicles.
- Check and record the current reading.
- Note the battery reserve capacity, amp hour rating. Refer to Battery Usage .
- If excessive current drain is not found at this time and there are no other apparent causes, complete the following:
- Using the MIN/MAX function of the digital multimeter, monitor the parasitic drain overnight or during the day. This will determine if something has been activated during that time frame.
- When the vehicle has an unacceptable amount of parasitic current drain, remove each fuse one at a time until the current drain falls to an acceptable level. This will indicate which circuit is causing the drain. Refer to Power Distribution Schematics in Wiring Systems to diagnose exactly which part of the suspect circuit is causing the parasitic drain. In some cases a non-fused circuit or component, such as a relay, is the cause of excessive parasitic current drain.
- Repeat the parasitic current drain test procedure after any repair has been completed to make sure that the parasitic current drain is at an acceptable level.
- When the cause of the excessive current drain has been located and repaired, remove the J 38758 .
- Connect the battery negative cable to the battery negative terminal.
| 15.1. | When there is a current reading on 2A or less, turn the J 38758 knob to the ON position. The electrical current will now pass through the switch. |
| 15.2. | Then switch the digital multimeter down to the 2A scale for a more accurate reading when the J 38758 knob is turned OFF. |
| 18.1. | Divide the reserve capacity by 4, amp hour rating by 2.4. |
| 18.2. | Compare this to the multimeter milliampere reading taken in the previous step. The parasitic current drain should not exceed this number. Example: If a battery has a reserve capacity of 100 minutes, (60 A/H) the current drain should not exceed 25 mA. |
Notice: The test switch must be in the ON position when removing the fuses in order to maintain continuity in the electrical system. This avoids damaging the digital multimeter due to accidental overloading, such as a door being opened to change a fuse.
Important: Removing fuses, relays, and connectors to determine the failure area may wake up modules. You must wait for these modules to go to sleep or use the sleep function on the scan tool.
