DTC 42

Code 42 - Electronic Spark Timing (EST):

Wiring Diagram For Code 42 - Electronic Spark Timing (EST):

CODE 42 - ELECTRONIC SPARK TIMING (EST)



Circuit Description:

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



Test Description:

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 CKT 424, 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 r module.

5. Confirms that Code 42 is a faulty ECM and not all intermittent in CKT'S 423 or 424.