Circuit Description
The Ignition Voltage is supplied to the Transmission Control Module (TCM) to indicate the status of the ignition switch. Battery voltage is supplied to the TCM on circuit 440 to maintain memory of learned functions and parameters.
If the TCM detects low voltage input, then DTC 75 sets.
Conditions for Setting the DTC
| • | The ignition is ON. |
| • | The engine speed is greater than 300 RPM. |
| • | System voltage is: |
| - | Less than 7.3 volts at -40°C (-40°F) or |
| - | Less than 10.3 volts at 90°C (194°F) |
| - | or |
| - | Less than 11.7 volts at 150°C (304°F) |
| • | The above conditions are met for 4 seconds. |
Action Taken When the DTC Sets
| • | The TCM does not illuminate the Malfunction Indicator Lamp (MIL). |
| • | The PC Sol. Valve is turned OFF. |
| • | Soft landing to default 2nd gear. |
| • | Inhibit fourth gear and TCC. |
| • | DTC 75 is stored in TCM history. |
Conditions for Clearing the DTC
| • | The TCM clears the DTC from Current to History when the fault condition(s) no longer exist and the ignition switch is cycled OFF and then ON. |
| • | A scan tool can clear the DTC from Current and History status. The TCM clears the DTC from the TCM history if the vehicle completes 40 ignition cycles without a failure reported. |
| • | The TCM cancels the DTC default actions when the fault no longer exists and the ignition is cycled OFF and then ON. |
Diagnostic Aids
| • | Inspect the wiring at the TCM, the transmission connector and all other circuit connecting points for the following conditions: |
| - | A bent terminal |
| - | A backed out terminal |
| - | A damaged terminal |
| - | Poor terminal tension |
| - | A chafed wire |
| - | A broken wire inside the insulation |
| - | Moisture intrusion |
| - | Corrosion |
| • | Charging the battery with a battery charger and jumpstarting an engine may set DTCs. |
| • | If this DTC is set when an accessory is operated, inspect for faulty connections or an excessive current draw. |
| • | Inspect for faulty electrical connections at the starter solenoid. |
| • | Inspect for faulty electrical connections at the fusible link. |
| • | Inspect for loose or damaged terminals at the generator. |
| • | Inspect the generator belt wear condition and tension. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests the charging system voltage.
-
This step tests the battery voltage input at the TCM.
-
This step tests the ignition voltage inputs at the TCM.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||
2 |
Important:: Before clearing the DTC's, record the Current and History DTC's information for reference. The Clear Info function erases the stored Current and History DTC from the TCM. Is the voltage higher than the specified value? | 10.5 volts | Go to Engine Electrical | |||||
Is the J 39200 DMM battery voltage within the specified value? | 13 - 15.5 volts | Go to Engine Electrical | ||||||
4 |
Is the Scan Tool voltage within 0.5 volts of the J 39200 DMM voltage? | -- | System Checks OK Refer to Diagnostic Aids | |||||
Is the J 39200 DMM voltage within 0.5 volts of the battery voltage reading from Step 3? | -- | |||||||
6 | Repair the high resistance condition in circuit 440. Refer to Wiring Repairs . Did you repair the circuit? | -- | -- | |||||
Is the J 39200 DMM voltage within 0.5 volts of battery voltage from Step 3? | -- | |||||||
8 | Repair the high resistance condition in circuit 439. Refer to Wiring Repairs . Did you repair the circuit? | -- | -- | |||||
9 |
Did you find a condition? | -- | ||||||
10 | Replace the TCM. Refer to DTC 51 PROM Error TCM/PROM Replacement. Is the replacement complete? | -- | -- | |||||
11 | In order to verify your repair, perform the following procedure:
Is the Scan Tool ignition voltage within the specified value? | 12 - 16 volts | System OK | Begin Diagnosis again. |
