74 - System Control Mode Timeout

SYSTEM CONTROL MODE TIME-OUT-74
For a complete wiring diagram, refer to Wiring Diagram Information.

When Monitored
Ignition on.

Set Condition
When the vehicle is in antilock control mode. Vehicle speed is above 4 MPH for 2 seconds. ABS mode is on continuous pressure control mode for an excessive period of time (two minutes).

Possible Causes
- INTERMITTENT EXCESSIVE DUMP TIME DTC
- WHEEL SPEED WIRING HARNESS AND CONNECTORS
- SUSPENSION
- TONE WHEEL
- WHEEL BEARING
- BRAKE SYSTEM MECHANICAL CONDITION
- BRAKE SWITCH SENSE CIRCUIT
- BRAKE SWITCH
- CONTROLLER ANTI-LOCK BRAKE

Diagnostic Test
1. BRAKE SYSTEM MECHANICAL CONDITION

NOTE: This DTC must be active before continuing, clear all DTC(s) and attempt to reset. Riding the brake for an extended period of time while driving can cause this DTC to set. If the DTC does not reset review with the customer driving habits.

Inspect the front and rear brakes for a mechanical condition that would cause any wheel(s) to lock-up during braking.
Inspect the Parking Brake to make sure it releases properly.

Were any problems found?
Yes >> Repair the braking system as necessary in accordance with the Service Information.
Perform ABS VERIFICATION TEST - VER 1. ABS Verification Test
No >> Go To 2

2. TONE WHEEL
Inspect each Tone Wheel for damage, missing teeth or looseness in accordance with the Service Information.

NOTE: The Tone Wheel Teeth should be perfectly square, not bent or nicked.

Were any problems found?
Yes >> Replace the Tone Wheel as necessary in accordance with the Service Information.
Perform ABS VERIFICATION TEST - VER 1. ABS Verification Test
No >> Go To 3

3. WHEEL BEARING
Inspect each wheel bearing for excessive run out or improper clearance in accordance with the Service Information.

Were any problems found?
Yes >> Repair or replace the wheel bearing(s) as necessary in accordance with the Service Information.
Perform ABS VERIFICATION TEST - VER 1. ABS Verification Test
No >> Go To 4

4. WHEEL SPEED SENSOR WIRING HARNESS AND CONNECTORS
Start the engine.
With the scan tool, monitor the output of each Wheel Speed Sensor.
Raise and properly support the vehicle.

WARNING: BE SURE TO KEEP HANDS, FEET AND CLOTHING CLEAR OF ROTATING COMPONENTS.

Allow the drive wheels to rotate.
Rotate the non-driven wheels by hand.
Wiggle test the Wheel Speed wiring harnesses and connectors.
Look for any excessive variations in sensed wheel speed.

Were any problems found?
Yes >> Repair the wiring harness or connectors as necessary in accordance with the Service Information.
Perform ABS VERIFICATION TEST - VER 1. ABS Verification Test
No >> Go To 5

5. LOADED WHEEL BEARING/SUSPENSION CONCERN

CAUTION: Make sure that the vehicle has braking capability before performing a road test.

NOTE: Have an assistant drive the vehicle while monitoring the scan tool.

With the scan tool, monitor the output of each Wheel Speed Sensor.
Road test vehicle so wheel bearings and suspension are loaded.
Look for any excessive variations in sensed wheel speed.

Were any problems found?
Yes >> Repair as necessary in accordance with the Service Information.
Perform ABS VERIFICATION TEST - VER 1. ABS Verification Test
No >> Go To 6

6. BRAKE SWITCH SENSE CIRCUIT
NOTE: The brake lamps must be operating properly before confining.

NOTE: Riding the brake can cause this fault, a review of the customers driving habits may help in the diagnosing of this DTC.

With the DRBIII (R) in the Inputs/Outputs, monitor the Brake Switch state.
Apply and release the brake pedal.

Does the Brake Switch state on the DRBIII (R) match the actual pedal state?
Yes >> Replace the Controller Antilock Brake in accordance with the Service Information. refer to the symptom *Replacing the Controller Antilock Brake.
Perform ABS VERIFICATION TEST - VER 1. ABS Verification Test
No >> Repair the Brake Switch Sense circuit. If OK, replace the Brake Switch.
Perform ABS VERIFICATION TEST - VER 1. ABS Verification Test