DTC 18 - Pump Cam Reference Pulse Error: Notes

The optical sensor also provides a pump cam signal to the PCM by counting pulses on the sensor disk located in the injection pump. The pump cam reference signal is one of the most important inputs used by the PCM for timing and start of injection. DTC 18 will set when 8 cam reference pulses are missed for every crankshaft position pulse. PCM will default to backup fuel.

1. This step determines if DTC 18 is the result of a hard failure or an intermittent condition.
2. This step checks the 5-volt reference circuits.
3. This step checks the ground circuit.
4. This step checks if the sensor is sending a signal back to the PCM and if an open is present in the cam signal circuit.