Q DTC C1185

NOTE: Refer to the PINPOINT TEST section of the Flow of Diagnosis before beginning this pinpoint test. Flow of Diagnosis

NORMAL OPERATION:
The anti-lock brake control module conducts a valve function test every time the vehicle is keyed "ON", and the wheels exceed 6.4 km/h (4 mph) for the first time. In order to perform a valve function test, the anti-lock relay is commanded "ON" by the anti-lock brake control module to supply B+ to the valve solenoids and pump motor. The anti-lock relay is verified for proper operation by the anti-lock brake control module during this test. A passive test of the anti-lock relay is conducted by the anti-lock brake control module to check for open contacts during the time the anti-lock relay is commanded "ON" by the anti-lock brake control module.

FAULT DESCRIPTION:
A shorted anti-lock relay diagnostic trouble code (DTC) C1185 is generated by the anti-lock brake control module's detection of 0 voltage at all of the solenoids when they are expected to be at B+.

POSSIBLE CONTRIBUTING CONDITIONS:
- Open anti-lock relay coil or non-closeable contacts.
- Blown 60A ABS maxifuse in the main fuse junction panel.
- Blown 15A HEGO fuse in the interior fuse Junction panel.
- Circuit 710 (W) and/or 900 (BK/R).
- Defective circuit within the anti-lock brake control module.
- Defective circuit within the hydraulic anti-lock actuator.
- Battery voltage is below the anti-lock relay pull in point, but is high enough to allow the anti-lock brake control module to continue to operate.

Q1- Check Fuses
- Check 60A ABS fuse.
- Check 15A HEGO fuse.
- Are fuses OK?
YES - Reinstall fuses and go to Q5.
NO - If 60A ABS fuse is blown to to Q2.
- If 15A HEGO fuse is blown go to Q3.

Q2- Check for Short
- Disconnect connector from anti-lock relay.

ABS Relay Circuit Test. Pin 87:

- Measure the resistance between the ABS relay connector pin 87, circuit 900 (BK/R) and ground.
- Is the resistance greater than 10,000 ohms?
YES - Replace the 60A ABS fuse and go to Q4.
NO - Repair circuit 900 (BK/R) and go to Q10.

Q3- Check for Short
- Disconnect connector from anti-lock relay.
- Disconnect connector from anti-lock brake control module.

ABS Relay Circuit Test. Pin 85:

- Measure the resistance between the anti-lock relay pin 85, circuit 710 (W) and ground.
- Is the resistance greater than 10,000 ohms?
YES - Replace the 15A HEGO fuse and go to Q4.
NO - Repair circuit 710 (W) and go to Q10.

Q4- Check Power Supply
- Disconnect connector from anti-lock relay.
- Turn ignition switch to "RUN".
- Measure the voltage between the anti-lock relay connector pin 87, circuit 900 (BK/R) and ground.
- Measure the voltage between the anti-lock relay connector pin 85, circuit 710(W) and ground.
- Are the voltages greater than 10 volts?
YES - Go to Q5.
NO - If voltage is 0 volts, Repair defective circuit then go to Q10.
- If voltage is greater than 0 volts but less than 10 bolts, there is insufficient voltage to pull in the anti-lock relay. Check the charging system and battery. Refer To: Starting and Charging.

Q5- Check Anti-Lock Relay
- Test the anti-lock relay. Testing and Inspection
- Is the relay OK?
YES - Go to Q6.
NO - Replace the anti-lock relay and go to Q10.

Q6- Check Relay Coil Circuit
- Disconnect connector C386 from anti-lock control module and connect breakout box and adapter.

ABS Relay Circuit Test. Pin 86:

- Measure the resistance between breakout box pin 4 and the anti-lock relay connector pin 86.
- Measure the resistance between breakout box pin 4 and pin 1.
- Is the resistance less than 5 ohms between breakout box pin 4 and anti-lock relay connector pin 86 and greater than 10,000 ohms between breakout box pin 4 and pin 1?
YES - Go to Q7.
NO - Repair circuit 908 (R/Y) and go to Q10.

Q7- Check Relay Power Outlet Circuit
- Disconnect both connectors from the hydraulic anti-lock actuator.

ABS Relay Circuit Test. Pin 30:

- Measure the resistance between breakout box pin 25 and anti-lock relay connector pin 30.
- Measure the resistance between breakout box pin 25 and pin 1.
- Is the resistance less than 5 ohms between breakout box pin 25 and anti-lock relay connector pin 30 and greater than 10,000 ohms between breakout box pin 25 and pin 1?
YES - Reconnect the anti-lock relay and hydraulic anti-lock actuator connectors and go to Q8.
NO - Repair circuit 907 (Y) and go to Q10.

Q8- Check Hydraulic Anti-Lock Actuator Circuits
- Install a jumper wire between breakout box pin 4 and pin 1.
- Turn ignition switch to "RUN".
- Measure the voltage between the following breakout box pins and pin 1 (ground):
- 28, 29, 30, 31
- 36, 37, 38, 39
- Turn ignition switch to "OFF".
- Were all voltages greater than 10 volts?
YES - Replace the anti-lock brake control module and go to Q10.
NO - Go to Q9.

Q9- Check Hydraulic Anti-Lock Actuator Power Supply
- Disconnect 12-pin hydraulic anti-lock actuator connector .
- Turn ignition switch to "RUN".

ABS HCU Power Test. Pins 3, 4, 5, 12:

- Measure the voltage between the following hydraulic anti-lock actuator connector pins and pin 1 (ground).
- 3, 4, 5
- 12
- Were all voltages greater than 10 volts?
YES - Replace the hydraulic anti-lock actuator and go to Q10.
NO - Repair circuit 907 (Y).

Q10- Verify Repair
- Restore vehicle. Reconnect all components.
- Clear all DTC's using the scan tool.
- Repeat the Drive Cycle Test.
- Retrieve DTC's using the scan tool.
- Is System Pass obtained?
YES - Stop. Repair is complete.
NO - If original code is retrieved, repeat Pinpoint Test Q.
- If a different DTC is retrieved, return to DTC Index.