P0370

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION
The optical sensor provides a high resolution signal to the Powertrain Control Module (PCM) by counting pulses on the sensor disk located in the injection pump. The high resolution is one of the most important inputs by the PCM for fuel control and timing. This test monitors the number of high resolution pulses which have been missed (not detected). It's based on a comparison between the number of pulses that were detected since the last pump cam pulse and the number of the pulses that should have occurred. This is a type A DTC.

CONDITIONS FOR SETTING THE DTC
A number of High resolution pulses (internal to PCM) per every 8 cam reference pulses.

ACTION TAKEN WHEN THE DTC SETS
Backup fuel.

CONDITIONS FOR CLEARING THE MIL/DTC
- The PCM will turn the MIL off after three consecutive trips without a fault condition.
- A History DTC will clear when forty consecutive warm-up cycles that the diagnostic does not fail (coolant temperature has risen 5°C (40°F) from start up coolant temperature and engine coolant temperature exceeds 71°C (160°F) that same ignition cycle.

DIAGNOSTIC AIDS
When PCM is in backup fuel, fast idle and poor performance problems will exist. If P0251 is also stored, the snap shot mode on the scan tool should be used to properly identify fault. It is possible P0370 may set if the vehicle runs out of fuel.

TEST DESCRIPTION
Number(s) below refer to the Step number(s) on the Diagnostic Table.

2. This Step will determine if there is a 5 volt reference.
3. This Step checks the ground circuit.
4. This Step will check to see if the sensor is sending a signal back to the PCM.