Diagnosis & Testing: INTERMITTENTS

Most intermittent problems are caused by faulty electrical connections or wiring; however, a sticking relay or solenoid can cause a failure. When intermittent failure is encountered, check for fault messages stored in ECU. If fault messages are found, inspect related components and circuitry for poor connections. If no trouble codes are found, inspect suspect circuits as follows:

• Check for poor mating of connector halves, or terminals not fully seated in connector body (backed-out).
• Check for improperly formed or damaged terminals. Carefully reform all connector terminals of problem circuit to increase contact tension.
• Check for poor terminal-to-wire connection.
• Check for hydraulic system leaks.
• Damaged components, especially sensors and tone wheels.
• Excessive axle shaft runout.
• Regular brake system problems, non-ABS related.

If no obvious problem is found, erase Diagnostic Trouble Codes (DTCs). Turn ignition on and wiggle suspected wire harness and connectors. Periodically recheck for new DTCs as system is checked.