• | 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+ | B1370 06, B1380 06, U0100-U0299, 2, 4 | B1370 06, B1380 06, U0100-U0299 | -- | -- |
Accessory Voltage | B1370 06, B1380 06, U0100-U0299, 2, 4 | B1380 06, 1 | B1380 01, P1629, 1 | -- |
Ignition 1 Voltage | B1370 06, B1380 06, U0100-U0299, 2, 4 | B1370 06, 1 | B1370 01, U0100-U0299, 1, 2 | -- |
Off/Run/Crank Voltage | B1370 06, B1380 06, U0100-U0299, 2, 4 | 1 | 1 | -- |
Run/Crank Ignition 1 Voltage | B1428, 3 | B1370 06 | -- | -- |
Accessory Wakeup Serial Data | U1814, 3 | U0100-U0299, P0513 00 | -- | -- |
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This vehicles power mode master (PMM) is the body control module (BCM). The ignition switch is a low current switch with multiple discrete ignition switch signals to the PMM for determination of the power mode. The PMM receives the ignition switch signals, and additionally a reference voltage signal from the BCM, through the ignition switch, and back to the BCM. There are redundancies within the PMM system that can allow operation of certain subsystems when there are faults in the ignition switch circuits. Other information such as serial data input from other modules and DTCs is also used to determine what power mode signals and information is transmitted by the PMM. The BCM logic uses all this information to identify the operators desired power mode and activate specific discrete signals, and serial data messages for the operation of many 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 see from its own connections.
The PMM will activate relays and other direct outputs of the PMM as needed according to the calculated power mode. Several relays controlled by the BCM are switched ignition voltage outputs the are pass through circuits within the BCM directly from the ignition switch. If these circuits short to ground, the fuse to the ignition switch will open.
Ignition switch is in the OFF or ACC positions.
Ignition switch is in the START position.
Ignition 1 voltage circuit is shorted to voltage for more than 2 seconds.
• | Ignition 1 voltage circuit is open for more than 2 seconds. |
• | Ignition 1 voltage, accessory voltage, or off/run/crank voltage circuit shorted to ground. |
• | Battery positive voltage circuit of the ignition switch open or shorted to ground. |
• | Run crank relay coil control circuit open (including relay coil and ground). |
• | A current DTC clears when the malfunction is no longer present. |
• | A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction. |
• | A short to ground in the accessory wakeup 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 Body Control Module Power Mode data display parameters listed in Circuit/System Verification will determine if there is a power mode fault. |
Power Mode Description and Operation
Control Module References for scan tool information
⇒ | If either of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle. |
Ignition Switch Position | Current Power Mode | Ignition Off/Run/Crank (Off/Run Crank Voltage Circuit) | Ignition Accessory/Run (Accessory Voltage Circuit) | Ignition Run/Crank (Ignition 1 Voltage Circuit) |
---|---|---|---|---|
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 |
Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
⇒ | If the fuse is open, test the following circuits for a short to ground, if all circuits test OK, replace the BCM. |
• | B+ to the ignition switch |
• | Accessory voltage |
• | Off/Run/Crank voltage |
• | Ignition 1 voltage |
• | Accessory wakeup serial data (BCM output) |
• | Run/crank ignition 1 voltage (BCM output) |
⇒ | If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. |
Important: 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. |
• | Ignition key resistor signal terminal 4 |
• | Off/Run/Crank voltage terminal 2 |
• | Accessory voltage terminal 21 |
• | Ignition 1 voltage terminal 14 |
⇒ | If greater than specified, test the circuit for a short to voltage. |
• | Ignition key resistor signal, BCM terminal 4 and ignition switch terminal 6 |
• | Off/Run/Crank voltage, BCM terminal 2 and ignition switch terminal 5 |
• | Accessory voltage, BCM terminal 21 and ignition switch terminal 3 |
• | Ignition 1 voltage, BCM terminal 14 and ignition switch terminal 2 |
⇒ | If greater than specified, repair the circuit for open/high resistance |
⇒ | If less than specified, repair the signal circuit for a short to ground. |
Ignition Switch Position | Terminals 4 and 2 | Terminals 4 and 3 | Terminals 4 and 5 | Terminals 4 and 6 | Terminals 5 and 6 |
---|---|---|---|---|---|
Off Key Out | Infinite | Infinite | Infinite | Infinite | Infinite |
Off Key IN | Infinite | Infinite | < 5.0 Ohms | Infinite | Infinite |
Accessory | Infinite | < 5.0 Ohms | Infinite | Infinite | Infinite |
Run | < 5.0 Ohms | < 5.0 Ohms | Infinite | Infinite | < 5.0 Ohms |
Start | < 5.0 Ohms | Infinite | Infinite | Infinite | 1275-1325 Ohms |
⇒ | If any reading is not as specified, replace the ignition switch. |
Perform the Diagnostic Repair Verification after completing the repair.
• | Control Module References for BCM replacement, setup, and programming |