DTC 42

Code 42 Diagnostic Chart:

Code 42 Circuit Diagram:

CIRCUIT DESCRIPTION:

The fuel cut-off relay is supplied B+ by fuse 13, and grounded by the ECM driver when in a deceleration mode. The ECM senses a deceleration condition from the TPS and a tach. Signal above 2300 rpm. With the relay open, the fuel cut-off solenoid is de-energized and fuel flow is decreased. Code 42 sets if the voltage on the driver circuit remains "high" when commanded "low."

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Checks for short to voltage and for faulty ECM.

2. Code 42 means the ECM has sensed an open or short to voltage in the fuel cut-off relay circuits. This test checks for a shorted fuel cut-off relay.

3. Shorts to voltage may have caused damage to the ECM preventing Code 42 from being cleared.

DIAGNOSTIC AIDS:

Check for normal operation of TPS and idle switch. If ECM is receiving wrong signal from throttle switches a false deceleration could be sensed, Chart C-1A Throttle Position Sensor Check and Chart C-1B Idle Switch Check

If Code 42 is intermittent, Testing and Inspection