DTC 42

Fig. 045 - Wiring Diagram for Code 42 Electronic Spark Timing. VIN 3:

CODE 42

ELECTRONIC SPARK TIMING (EST)
3.8L "A & C" SERIES

FUEL INJECTION (PORT)

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

Fig. 044 - Chart - Code 42 Electronic Spark Timing:

1. Grounding the diagnostic terminal causes the ECM to set a fixed timing value, so it should change compared to the timing before grounding the diagnostic terminal. If it does, the EST system is working.
2. Jumpering "B" to "B" and "D" to "D" completes the reference circuit so the car will run. Measuring "A" voltage checks for an EST signal from the ECM.
3. Jumpering "A" to "A" completes the EST circuit, but with the by-pass circuit still open, the engine is running on module timing. Under this condition, the EST circuit is grounded by the HEI module so the EST voltage should now be less than .4 volts.
4. The test light serves as a jumper to apply voltage to the by-pass terminal so the module will switch to allow EST. The EST signal will no longer be grounded, so there should be a voltage reading on the EST circuit.
5. Checks the by-pass circuit in ECM. With engine running, it should normally read 4 to 5 volts.