C1273

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Part 2 Of 2:

CIRCUIT DESCRIPTION
When the Electronic Brake Traction Control Module (EBTCM) commands the electronic brake control relay ON, B+ is supplied through the EBTCM connector C1 terminal Be to the MAGNASTEER actuator connector terminal A. Ground/control for the MAGNASTEER actuator is provided through the EBTCM connector C1 terminal B7 to MAGNASTEER actuator connector terminal B. The EBTCM controls the amount of current supplied to the MAGNASTEER actuator based on the input from the wheel speed sensors.

CONDITIONS FOR SETTING THE DTC
The EBTCM sets DTC C1273 when these conditions are met:
- The electronic brake control relay is commanded ON.
- Vehicle speed is above 16 km/h (10 mph) when the MAGNASTEER actuator is commanded ON.
- Commanded current is greater than 0.5A and the sense current is less than half the command current.
- The MAGNASTEER actuator control circuit is below 1.7V (B+ expected).

ACTION TAKEN WHEN THE DTC SETS
- The EBTCM stores DTC C1273 in memory.
- The Antilock Brake System (ABS) and Variable Effort Steering (VES) are disabled.
- The amber ABS warning indicator lamp turns on.
- The power steering returns to medium assist.
If the malfunction occurs during an ABS event, the ABS disable action is delayed until the ABS event is over.

CONDITIONS FOR CLEARING THE DTC
DTC C1273 setting conditions no longer exist when the ignition switch is turned off.

DIAGNOSTIC AIDS
The following conditions may cause this malfunction to occur:
- An open or short to ground in circuit 345.
- An open or short to ground in circuit 1787.
- A poor connection.
- Rubbed-through wire insulation.
- A broken wire inside the insulation.
- Backed out terminals.
- Improper mating.
- Broken locks.
- Improperly formed or damaged terminals.
- Poor terminal to wiring connections.
- Physical damage to the wiring harness.
Ensure that all the ABS DTCs are diagnosed and corrected prior to cleaning VES DTCs. Cleaning the VES DTCs will automatically clear the ABS DTCs resulting in a loss of DTC history data. Refer to Diagnostic System Check - ABS in Antilock Brake System for more information.
Use the enhanced diagnostic function of the scan tool in order to measure the frequency of the malfunction. Refer to Enhanced Diagnostics for more information.

IMPORTANT: Zero the J 39200 (DMM) test leads prior to making any resistance measurements. Refer to J 39200 user's manual.

Clear the DTCs after completing the diagnosis. Test drive the vehicle for three drive cycles in order to verify that the DTC does not reset. Use the following procedure in order to complete one drive cycle:
1. Start the vehicle.
2. Drive the vehicle over 16 km/h (10 mph).
3. Stop the vehicle.
4. Turn the ignition switch off.

TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
2. This step checks for proper correct feedback values.
3. This step checks for an open in circuit 345.
4. This step checks for a short ground in circuit 345.
5. This step checks for an open in circuit 1787.
6. This step checks for a short ground in circuit 1787.
7. This step checks for a faulty MSVA actuator.
8. This step checks for a faulty MSVA actuator.
9. This step determines whether the EBTCM is faulty or the condition is intermittent.