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Use a digital volt meter with a min/max function to monitor the battery voltage PCM at fuse 22 in the inside fuse box. The circuit should maintain full battery voltage any time the key is on. If the voltage drops when the problem occurs, swap the PCM power relay with a similar relay and recheck operation. If the problem is gone, replace the faulty relay.
If battery voltage stays consistent on the Red wire PCM power, monitor the 5 V reference voltage on the Brown/White wire at pin 90 of the PCM connector. If the voltage drops from 5 V when the problem happens, suspect a shorting sensor, or a short to ground in the reference voltage circuit. Try disconnecting each sensor on the reference voltage circuit. Start with disconnecting the exhaust
backpressure and Injection Control Pressure (ICP) sensors one at a time and recheck operation. If the problem is gone after disconnecting a sensor, replace and recheck operation. If the VEEF voltage stays steady at 5 V, then shake the wire harness to each sensor to try to make this occur. Monitor the voltage drop on the grounds at pins 51, 76, 77, and 103 Black/White (BK/WH) wires and pin 25 Black/Light Blue (BK/LB)at the PCM wires when the problem happens. Repair or add grounds to the circuits as needed and recheck operation.
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