12a. Low Idle Stability (ICP Pressure)

12A. LOW IDLE STABILITY (ICP PRESSURE)

NOTE: The engine oil temperature must be above 80°C (176°F).

Purpose:
The purpose of this test is to determine if idle stability or low power is caused by a stuck or dirty injection pressure regulator (IPR) or faulty ICP signal.

Low Idle Stability (ICP Pressure)
- Check at low idle and EOT above 80°C (176°F)
- Monitor the ICP and RPM PIDS with the scan tool.







If engine RPM is unstable, disconnect the ICP sensor.
- ICP defaults to 6.0 MPa (870 psi) when disconnected.
- If RPM smooths out, the ICP sensor or circuit is suspect.
- If RPM is still unstable, connect the ICP sensor and go to step 12b. 12b. Injection Pressure Regulator Test

Recommended Procedure:

- Connect the scan tool.
- Key ON, engine OFF.
- Monitor the ICP voltage. If the voltage is not between 0.15 volts to 0.35 volts GO to Pinpoint Test Q. Test Q: Injection Control Pressure (ICP) Sensor
- Key ON, engine running.
- Idle the engine until the EOT is greater than 80°C (176°F).
- With the engine running, access the monitor the ICP, IPR, and the RPM PIDs.
- Compare the ICP PID to the specification.
- Disconnect the ICP sensor connector. Verify the ICP PID is 0 volts.
- Operate the engine at low idle speed.

If the low idle speed stabilizes with the ICP sensor disconnected, the problem is most likely in the ICP sensor circuit. Go To Pinpoint Test Q. Test Q: Injection Control Pressure (ICP) Sensor

If the RPM does not stabilize, reconnect the sensor and GO to Injector Pressure Regulator Test.

Possible Causes:
- Debris stuck in the IPR
- ICP sensor
- Circuitry

Tools Required:
Scan tool