Code 42, Crank Angle Sensor Circuit, No Signal For 3 Seconds: Notes

When distributor shaft rotates, a fluctuating magnetic field is generated due to changes in air gap between crank angle sensor and distributor shaft signal rotor. As a result, a small AC voltage is induced in the crank angle sensor. This ignition reference signal is sent to the ECM on ECM terminal No. B1 and B9. ECM monitors the AC voltage between these terminals. The ECM uses this signal in determining when to fire the ignition coil and fuel injector.

Code 42 will set when ignition signal is not present at the ECM for3 seconds.

1. Crank angle sensor contains a coil of very small wire. Its DC resistance is checked on this step.
2. This checks for a proper AC signal voltage being produced. When distributor shaft turns, the crank angle sensor acts as an AC voltage signal generator.
3. This step checks to see if proper AC signal voltage is getting through to the ECM connector.