N DTC C1178, C1236 (Dynamic)
NOTE: Refer to the PINPOINT TEST section of the Flow of Diagnosis before beginning this pinpoint test. Flow of DiagnosisNORMAL OPERATION:
The anti-lock brake control module constantly monitors all brake anti-lock sensor signals to ensure that they are proper and do not drop out, have sudden spikes or indicate a situation that is not physically possible.
FAULT DESCRIPTION:
Diagnostic trouble codes (DTC's) are generated by the anti-lock brake control module's detection of a missing, erratic or otherwise improper wheel speed signal from the LR brake anti-lock sensor. The DTCs are set for specific faults at various vehicle speeds. DTC C1178 is generated when the anti-lock brake control module detects that the LR brake anti-lock sensor signal has dropped out or is erratic for a significant period of time. DTC C1178 is only set when the LR brake anti-lock sensor indicates speed greater than 32 km/h (20 mph) with the brake applied or greater than 21 km/h (12 mph) with the brake released. DTC C1236 is generated when the anti-lock brake control module detects that the LR brake anti-lock sensor signal is missing or very low (less than 6.4 km/h [4 mph]) while the other brake anti-lock sensor signals indicate a speed greater than 12.9 km/h (8 mph). At the same time the anti-lock brake control module checks to make sure that drivetrain spin up is not occurring.
NOTE: More than one DTC may be stored for a given failure.
NOTE: DTCs C1178 and C1236 can NOT be set with the vehicle not moving. The vehicle should be driven when attempting to duplicate the concern. If DTCs C1178 and C1236 are set, then the anti-lock brake warning indicator will illuminate and the anti-lock control will be disabled. If the fault is corrected and the signal appears normal, the anti-lock brake warning indicator will be turned "OFF" and the anti-lock control will be enabled. DTCs are stored each time the anti-lock brake warning indicator turns "ON" for any of the above reasons.
POSSIBLE CONTRIBUTING CONDITION:
- Damaged left rear brake anti-lock sensor indicator.
- Weak left rear brake anti-lock sensor.
- Incorrect LR brake anti-lock sensor air gap.
- Excessive axle vibration.
- Intermittent short or open in circuit 916 (BK/R) or circuit 915 (R/BL).
- Disturbances caused by ignition or Radio Frequency Interference (RFI).
- Defective trigger circuit in the anti-lock brake control module.
N1- Retrieve DTC's
- - Turn ignition switch to "OFF".
- Connect scan tool to Data Link Connector (DLC).
- Turn ignition switch to "RUN".
- Retrieve DTC's using the scan tool.
- Is DTC C1175 retrieved?
YES - Go to Pinpoint test M to Diagnose DTC C1175. Ignore all other DTC's. M DTC C1175 (Static)
NO - If DTC C1178 and/or C1236 is/are retrieved, go to N2.
N2- Repeatability Test Drive (Mismatched Output)
NOTE:
- Recording all speeds for later plotting will eliminate the need of monitoring the scan tool while driving.
- If a hard turn is made, some variation between all four sensors is expected.
- Select all four wheel speed signals from the scan tool PID index.
- Use scan tool to monitor PID's while driving the vehicle at various speeds and over rough roads.
- Does the LR brake anti-lock sensor signal consistently match the others?
YES - Concern is intermittent, go to N8.
NO - Concern is repeatable, go to N3.
N3- Check for Internal Sensor Short
- Disconnect LR anti-lock brake sensor.
- Measure Resistance between each sensor pin and ground.
- Does continuity exist?
YES - Replace the LR anti-lock sensor and go to N14.
NO - Go to N4.
N4- Check LR Sensor for Open
- Measure the resistance between the terminals of the LR ABS Sensor connector.
- Is the resistance between 2400 and 2800 ohms?
YES - Go to N5
NO - Replace LR anti-lock sensor and go to N14.
N5- Check Air Gap
- Raise and support the vehicle.
NOTE: The air gap is NOT adjustable. Inspect components for looseness or damage if the air gap is not within specification.
- Measure ABS sensor air gap. The gap should be 0.76-1.27 mm (0.030-0.050 inch).
- Is the air gap within specification?
YES - Go to N6.
NO - Repair or replace components as necessary and go to N14.
N6- Check Components
NOTE: Examine all components carefully. Failure to properly diagnose component damage at this time will lead to unnecessary component replacement and wasted diagnostic time.
- Remove the LR anti-lock sensor. Rear
- Visually inspect the LR anti-lock sensor indicator, the sensor and sensor cable for signs of damage, corrosion or improper fit.
- Are the components OK?
YES - Reinstall the anti-lock sensor and go to N7.
NO - Replace or repair components as necessary and go to N14.
N7- Check Circuits
- Disconnect the LR anti-lock sensor.
- Disconnect connector C386 from anti-lock control module and connect breakout box and adapter.
- Measure for continuity between breakout box pin 21 and pin 34.
- Measure for continuity between breakout box pin 21 and ground.
- Measure for continuity between breakout box pin 34 and ground.
- Does continuity exist?
YES - Go to N8.
NO - Repair Circuit 916 (BK/R) and/or 915 (R/BL) and go to N14.
N8- Begin intermittent Diagnosis
- Disconnect the LR anti-lock sensor.
- Measure the Resistance between the anti-lock sensor terminals (component side).
- Wiggle sensor cable along its entire length.
- Is the resistance measurement erratic during the test?
YES - Replace the anti-lock sensor and go to N14.
NO - Go to N9.
N9- Check for Intermittent LR Anti-Lock Sensor Open
NOTE: If at first the resistance measurement is 2400-2800 ohms, drive the vehicle over rough roads while an assistant monitors the reading for any change. This procedure is recommended to detect intermittent sensor coil failures. Normal brake applications will heat the sensor coil to help bring out intermittent high resistance faults.
- Measure the resistance between the terminals of the LR brake anti-lock sensor connector.
- Is the resistance between 2400 and 2800 ohms?
YES - Go to N10.
NO - Replace the LR anti-lock sensor and go to N14.
N10- Check for Intermittent LR Anti-Lock Sensor Short
NOTE: Use the beeper function on the multimeter to help detect an intermittent short to ground.
- Measure for continuity between each terminal of the LR ABS Sensor and ground.
- Drive the vehicle over rough roads at various speeds while an assistant monitors the resistance.
- Is continuity ever indicated?
YES - Replace the LR anti-lock and go to N14.
NO - Go to N11.
N11- Check for Intermittent Open
- Disconnect connector C386 from anti-lock control module and connect breakout box and adapter.
- Install a jumper wire between the two pins of the LR ABS Sensor connector (harness side).
NOTE: Use the beeper function on the multimeter to help detect an intermittent open.
- Measure the resistance between breakout box pin 21 and pin 34.
- Drive the vehicle over a rough road while an assistant monitors the resistance.
- Is an intermittent open circuit found?
YES - Repair Circuit 916 (BK/R) and/or 915 (R/BL) and go to N14.
NO - Remove jumper wire and go to N12.
N12- Check Circuit for an Intermittent Short
NOTE: Use the beeper function on the multimeter to help detect changes in continuity.
- Measure the resistance between breakout box pin 21 and ground.
- Drive the vehicle over a rough road while an assistant monitors the resistance.
- Measure the resistance between breakout box pin 34 and ground.
- Drive the vehicle over a rough road while an assistant monitors the resistance.
- Is an intermittent open circuit found?
YES - If intermittent was detected on Pin 21 repair circuit 915 (R/BL) and go to N14.
- If intermittent was detected on Pin 34 repair circuit 916 (BK/R) and go to N14.
NO - Go to N13.
N13- Check Components
NOTE: Examine all components carefully. Failure to properly diagnose component damage at this time will lead to unnecessary component replacement and wasted diagnostic time.
- Remove the LR anti-lock sensor. Rear
- Visually inspect the LR anti-lock sensor indicator, the sensor and sensor cable for signs of damage, corrosion or improper fit.
- Are the components OK?
YES - Replace the anti-lock brake control module and go to N14.
NO - Replace or repair components as necessary and go to N14.
N14- Verify Repair
- Reconnect all disconnected components. Restore vehicle.
- 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 - Go to N15.
NO - If original code is retrieved, go to N2 and repeat Pinpoint Test N.
- If a different DTC is retrieved, return to DTC Index.
N15- Verification Test Drive
NOTE:
- Recording all speeds for later plotting will eliminate the need of monitoring the scan tool while driving.
- If a hard turn is made, some variation between all four sensors is expected.
- Select all four wheel speed signals from the scan tool PID index.
- Use scan tool to monitor PID's while driving the vehicle.
- Gradually and smoothly accelerate the vehicle from a stop to 32.2 km/h (20 mph) several times.
- Does the LR brake anti-lock sensor signal consistently match the others?
YES - Stop. Repair is complete.
NO - Concern is repeatable. Go to N3.