DTC 42

Fig. 004 - Wiring Diagram for Code 42 Electronic Spark Timing. VIN P:

CODE 42, ELECTRONIC SPARK TIMING (EST)

Code 42 means the ECM has seen a open or short to ground in the EST or bypass circuits.

Fig. 003 Chart - Code 42 Electronic Spark Timing:

1. Confirms Code 42 and that the fault causing the code is present.

2. Checks for a normal EST ground path through the ignition module. An EST CKT 423 shorted to ground will also read less than 500 ohms; however, this will be checked later.

3. As the test light voltage touches terminal D-5, the module should switch causing the ohmmeter to "overrange" if the meter is in the 1000-2000 ohms position. Selecting the 10-20,000 ohms position will indicate above 5000 ohms. The important thing is that the module "switched".

4. The module did not switch and this step checks for:
- EST CKT 423 shorted to ground.
- Bypass CKT 424 open.
- Faulty ignition module connection or module.

5. Confirms that Code 42 is a faulty ECM and not an intermittent in CKTs 423 or 424.