• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
B+ - Terminal 1 | B1370 06, B1380 06, U0100-U0299, 1, 5, 6 | B1370 06, B1380 06, U0100-U0299, 1 | -- | -- |
Ignition - Terminal 2 | B1370 06, B1380 06, U0100-U0299, 1, 5, 6 | B1370 06, 1 | B1370 01, U0100-U0299, 1, 6 | -- |
Ignition - Terminal 4 | B1370 06, B1380 06, U0100-U0299, 1, 5, 6 | B1380 06, 1 | B1380 01, P1629, 1 | -- |
Ignition - Terminal 5 | B1370 06, B1380 06, U0100-U0299, 1, 5, 6 | 1 | 1 | -- |
Ignition Key Resistor Signal | 1 | 1 | 1 | -- |
Ignition Voltage - BCM Terminal 21 X4 | B1428 00, 4 | 2 | 3 | -- |
Accessory Wakeup Serial Data, BCM Terminal 19 X4 | U1814, 4 | U0100-U0299, P0513 00 | -- | -- |
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The vehicle power mode master (PMM) is the body control module (BCM). The ignition switch is a low current switch with multiple discrete circuits to the BCM. The BCM logic uses the ignition switch positions to identify the operator's desired power mode and activate specific discrete signals, and serial data messages for the operation of different subsystems as necessary. Other modules which have switched voltage inputs may operate in a default mode if the PMM serial data message does not match what the individual module can detect from its own connections.
The PMM will activate relays and other direct outputs of the PMM as needed according to the calculated power mode. Some relays controlled by the BCM are switched ignition voltage outputs that are pass through circuits within the BCM directly from the ignition switch. If these circuits short to ground, the B+ circuit fuse to the ignition switch will open.
Ignition switch is in the RUN or CRANK positions.
Ignition switch is in the RUN or ACCESSORY positions.
Ignition switch is in the RUN position.
Ignition switch is in the CRANK position.
Ignition circuit is shorted to voltage.
• | Ignition circuit is open. |
• | Ignition circuit shorted to ground. |
• | B+ circuit of the ignition switch is open or shorted to ground. |
• | Ignition relay control circuit open, including relay coil and ground. |
Accessory circuit is shorted to voltage.
• | Accessory circuit is open. |
• | Ignition or accessory circuit shorted to ground. |
• | B+ circuit of the ignition switch is open or shorted to ground. |
BCM detects an open or short to voltage on the off/run/crank signal circuit when both ignition ACCESSORY/RUN and ignition RUN/CRANK parameters are active.
BCM detects an open on the B+ circuit to the ignition switch while the engine is running.
Off/run/crank signal circuit is shorted to voltage.
Off/run/crank signal circuit is open.
• | The BCM operates in a fail-safe power mode dependent on the last valid power mode detected and the state of the engine run flag data on the serial data communications circuits. |
• | The other modules on the vehicle operate in a fail-safe power mode dependent on the last valid power mode transmitted by the BCM and the state of the engine run flag on the serial data communications circuits. |
• | The condition responsible for setting the DTC no longer exists. |
• | A history DTC will clear once 50 consecutive malfunction-free ignition cycles have occurred. |
• | A short to ground in the accessory wake up serial data circuit will cause an open fuse to the ignition switch. DTC U1814 should be current. |
• | A short to ground in the run/crank ignition 1 voltage circuit of the run crank relay will cause an open fuse to the ignition switch. DTC B1428 should be current. |
• | The power modes and controls are determined using BCM logic. Comparing the BCM Power Mode data display parameters listed in Circuit/System Verification will determine if there is a power mode fault. |
Retained Accessory Power Description and Operation
Control Module References for scan tool information
⇒ | If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for diagnosis. |
Ignition Switch Position | Current Power Mode | Ignition Off/Run/Crank (Ignition Switch, Terminal 5) | Ignition Accessory/Run (Ignition Switch, Terminal 4) | Ignition Run/Crank (Ignition Switch, Terminal 2) |
---|---|---|---|---|
Off Key Out | Off | Key Out/ACC | Inactive | Inactive |
Off Key IN | Off | Key In/Off | Inactive | Inactive |
Accessory | Accessory | Key Out/ACC | Active | Inactive |
Run | Run | Run | Active | Active |
Start | Crank Request | Crank | Inactive | Active |
⇒ | If any parameters are incorrect in any key position, proceed to the Circuit/System Testing. |
Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
⇒ | If the fuse is open, test the following circuits at the ignition switch for a short to ground, if all circuits test OK, replace the BCM. |
• | B+ - Terminal 1 |
• | Ignition - Terminal 2 |
• | Ignition Switch - Terminal 4 |
• | Ignition Switch - Terminal 5 |
• | Ignition - BCM terminal 19, X4 |
• | Accessory Wakeup Serial Data - BCM terminal 21, X4 |
⇒ | If greater than the specified range, replace the Key In Switch. |
⇒ | If less than the specified range, replace the Key In Switch. |
⇒ | If not the specified value, test the circuit for an open/high resistance. |
Note: The ignition switch component test must be preformed before proceeding with this test to verify the integrity of the switch.
⇒ | If the ignition switch fails, replace the ignition switch. |
• | terminal 2 |
• | terminal 4 |
• | terminal 14 |
• | terminal 21 |
⇒ | If not the specified range, test the circuit for a short to voltage. |
• | terminal 2 |
• | terminal 4 |
• | terminal 14 |
• | terminal 21 |
⇒ | If not the specified range, test the circuit for a short to voltage. |
• | Ignition key resistor signal Terminal 4 and Terminal 6 |
• | Off/Run crank Terminal 2 and Terminal 5 |
• | Off/Run crank Terminal 2 and Terminal 3 |
• | Accessory voltage Terminal 21 and Terminal 4 |
• | Ignition 1 voltage Terminal 14 and Terminal 2 |
⇒ | If not the specified range, test the circuit for open/high resistance. |
⇒ | If not the specified value, test the signal circuit for a short to ground. |
Using the Resistance Test below, verify the resistance between the pins of the ignition switch match the chart below while cycling the key to each switch position listed.
⇒ | If any reading is not within the specified range, replace the ignition switch. |
Ignition Switch Position | Pins 1 and 4 | Pins 1 and 2 | Pins 1 and 3 | Pins 5 and 6 |
---|---|---|---|---|
Off Key Out | Infinite | Infinite | Infinite | Infinite |
Off Key IN | Infinite | Infinite | < 5.0 Ω | Infinite |
Accessory | < 5.0 Ω | Infinite | Infinite | Infinite |
Run | < 5.0 Ω | < 5.0 Ω | Infinite | < 5.0 Ω |
Start | Infinite | < 5.0 Ω | Infinite | 1275-1325 Ω |
Perform the Diagnostic Repair Verification after completing the repair.
• | Control Module References for module replacement, setup, and programming |