Code 42
Code 42 is a diagnostic trouble code related to the electronic spark timing circuit on the Pontiac Fiero.
Code 42 indicates that the ECM has detected a problem in the electronic spark timing system.
Overview
The Fiero ignition system uses electronic spark timing control. Under normal operation, the ECM can control ignition timing through the ignition module and related wiring.
Code 42 is set when the ECM detects an unexpected condition in the electronic spark timing circuit. This may involve the ignition module, ECM, wiring, connectors, or related ignition-control circuits.
Flash pattern
Code 42 is displayed as:
- Four flashes
- Pause
- Two flashes
This represents code 42.
Animated flash pattern:
Meaning
Code 42 usually indicates an electronic spark timing circuit problem.
Possible causes include:
- Faulty ignition module
- Ignition module wiring problem
- Poor ignition module connector contact
- ECM wiring problem
- Poor ECM connector contact
- Faulty ECM
- Incorrect or damaged ignition wiring
- Poor grounds
- Previous-owner wiring modifications
Symptoms
Possible symptoms may include:
- Check engine light
- No-start condition
- Stalling
- Intermittent shutdown
- Poor drivability
- Misfire
- Poor acceleration
- Hard starting
- Engine starts but runs poorly
- Timing-related drivability problems
Diagnosis
Basic diagnostic checks include:
- Confirm that Code 42 is present.
- Inspect the ignition module connectors.
- Inspect ignition wiring for damage.
- Check for poor connector contact or corrosion.
- Check engine and ECM grounds.
- Check for other stored trouble codes.
- Check ignition module operation.
- Check ECM connector condition.
- Check for previous wiring repairs or modifications.
- Verify ignition timing and related ignition-system condition if applicable.
Ignition module
The ignition module is a common part to inspect when diagnosing Code 42, but Code 42 should not automatically be treated as a failed ignition module.
Wiring, connectors, grounds, ECM connections, and related ignition components should also be checked.
Related topics:
Electronic spark timing
The electronic spark timing system allows the ECM to control ignition timing during normal operation.
A problem in this circuit can affect ignition timing, drivability, starting, and engine operation.
Related topics:
Notes
Code 42 can be intermittent. Heat, vibration, poor connectors, old wiring, or ignition module problems may cause the code to appear only under certain conditions.
If the car stalls when hot and restarts after cooling, the ignition module, pickup coil, wiring, and related connectors should be inspected carefully.