Tip# 17: Check engine light code 42 for early 90s Chevy 3.1L engines

This code calls for ESC (electronic spark control) circuit failure which deals primarily with ignition. In other words, ignition parts that help produce spark such as ignition module, plug wires and coil. In this problem, the engine has no distributor and you can expect to investigate the crank sensor which is located either in the front or rear of the engine.

Symptoms:

Code 42 when accessed
Intermittent no start with misfire and hesitation
Starts and idles fine but as soon as you put it in drive, engine stalls

Normally, the symptom looks like a trany tcc (trany torque converter) problem if there is no code 42 code which is ignition related. Since the engine has a crank sensor, begin by checking for ac voltage on the sensor terminals while cranking. If no reading, either it has bad wiring or bad ecm (computer) provided there is 12 volt supply going to the ignition module. If there is an ac reading, the crank sensor is probably defective and you can check that by comparing the resistance with a new crank sensor. To save time, always replace the crank sensor and ignition module at the same time since they always work together. Once replaced, reset the codes and verify if the same code 42 comes back.

Notes:

1.) This check engine code is easily fixed provided you have a wiring diagram to trace the ignition components. Contact your local Chevy dealer or see ATS.

2.) This code problem assumes that the ignition coil and plug wires are tested OK.

3.) On Chevy Lumina 3.1L engines, there is a common wiring short always occurring between the crank sensor and ignition module connections.