Intermittents

4L60-E AUTOMATIC TRANSMISSION

DEFINITION
Problem may or may not turn "ON" the Malfunction Indicator Lamp (MIL) or store a DTC.

PRELIMINARY CHECKS
^ Perform the careful visual / physical checks as described in Preliminary Checks.
^ DO NOT use the diagnostic trouble code charts for intermittent problems. The fault must be present to locate the problem. If a fault is intermittent, use of diagnostic trouble code charts may result in replacement of good parts.

FAULTY ELECTRICAL CONNECTIONS OR WIRING
^ Most intermittent problems are caused by faulty electrical connections or wiring. Perform careful visual / physical check as described in Preliminary Checks.

- Poor mating of the connector halves or terminal not fully seated in the connector body (backed out)
- Improperly formed or damaged terminal. All connector terminals in the problem circuit should be carefully replaced to ensure proper contact tension.
- Poor terminal to wire connection. This requires removing the terminal from the connector body to check.

ROAD TEST
^ If a visual / physical check does not find the cause of the problem, the vehicle can be driven with a voltmeter connected to a suspected circuit. A Tech 1 can also be used to help detect intermittent conditions. An abnormal voltage, or scan reading, when the problem occurs, indicates the problem may be in that circuit. If the wiring and connectors check OK, and a diagnostic trouble code was stored for a circuit having a sensor, except for DTC's 44 and 45 substitute a known good sensor and recheck.

INTERMITTENT "MALFUNCTION INDICATOR LAMP (MIL)"
^ An intermittent MIL and no Diagnostic Trouble Codes (DTCs), may be caused by:

- Electrical system interference caused by a defective relay, control module driven solenoid, or switch. They can cause a sharp electrical surge. Normally, the problem will occur when the faulty component is operated.

- Improper installation of electrical devices, such as lights, 2-way radios, electric motors, etc.

- Ignition Control (IC) wires should be routed away from spark plug wires, ignition system components and generator. Wire for CKT 453 from control module to ignition system should be a good ground.

- Ignition secondary shorted to ground.

- CKT 419 Malfunction Indicator Lamp (MIL) or CKT 451 (diagnostic "test" terminal) intermittently shorted to ground.

- Control module grounds.

LOSS OF DIAGNOSTIC TROUBLE CODE MEMORY
^ To check for loss of diagnostic trouble code memory, disconnect Throttle Position (TP) sensor and idle engine until the "Malfunction Indicator Lamp" comes "ON." DTC 22 should be stored, and kept in memory when the ignition is turned "OFF" for at least 10 seconds. If not, the control module is faulty.