P2579

P2579-TURBOCHARGER SPEED SENSOR CIRCUIT PERFORMANCE

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The Turbocharger Speed Sensor is a variable reluctance speed sensor. It consists of a coil of wire and an iron core. The target on the turbocharger shaft is a ground flat surface in the center of the shaft. As the flat surface on the turbocharger shaft spins past the speed sensor, a signal is generated. The Powertrain Control Module (PCM) interprets this signal and converts it to a turbocharger speed reading. This monitor is a two trip fault. The MIL lamp will turn off once the diagnostic runs and passes in four consecutive drive cycles.

- When Monitored:
Engine running, turbo speed estimate is greater than a calibrated threshold.

- Set Condition:
The Powertrain Control Module (PCM) calculates an estimated turbo speed. The fault is activated when the difference of speed between the Turbo Speed Sensor and the turbo speed estimate is greater than a calibrated value. The fault is also activated if the Turbo Speed Sensor reading goes above a calibrated limit.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. DTC ACTIVE
1. With vehicle in park/neutral, use the accelerator pedal to accelerate the engine speed to 3100-3200 RPM and hold the engine speed for at least 60 seconds.
2. Return to idle for 60 seconds and then repeat.

Does P2579 become active?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test

2. INCORRECT BOOST PRESSURE SENSOR INSTALLED
1. The CAC/Boost Pressure Sensor and Intake Air Temperature/Intake Air Pressure Sensors are similar but have different part numbers. If the Boost Pressure Sensor was replaced with the wrong part, this DTC can be set.
2. Verify the part number of the Boost Pressure Sensor.

Is the Boost Pressure Sensor part number correct?

Yes

- Go To 3

No

- Replace the Boost Pressure Sensor with the correct part.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

3. TURBOCHARGER SPEED SENSOR
1. Turn the ignition off.
2. Disconnect the Turbocharger Speed Sensor harness connector.

NOTE: Check connectors - Clean/repair as necessary.

3. Measure the resistance of the Turbo Speed Sensor by probing (K540) Turbo Speed Sensor Signal circuit and the (K541) Turbo Speed Sensor ground circuit at the Turbocharger Speed Sensor.

Is the resistance between 600 and 1600 Ohms?

Yes

- Go To 4

No

- Replace the Turbocharger Speed Sensor.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

4. CHECK FOR HIGH RESISTANCE IN THE (K540) TURBO SPEED SIGNAL CIRCUIT
1. Disconnect the PCM C1 harness connector.
2. Measure the resistance of the (K540) Turbo Speed Sensor Signal circuit between the PCM C1 harness connector and the Turbocharger Speed Sensor harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Repair the (K540) Turbo Speed Sensor Signal circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 5

5. CHECK FOR HIGH RESISTANCE IN THE (K541) TURBO SPEED SENSOR RETURN CIRCUIT
1. Measure the resistance of the (K541) Turbo Speed Sensor Return circuit between the Turbo Speed Sensor harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 6

No

- Repair the (K540) Turbo Speed Sensor Signal circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

6. POWERTRAIN CONTROL MODULE
1. Reconnect the PCM C1 harness connector.
2. Start the engine.
3. With vehicle in park/neutral, use the accelerator pedal to accelerate the engine speed to 3100-3200 RPM and hold the engine speed for at least 60 seconds.
4. Return to idle for 60 seconds and then repeat.

Does DTC P2579 become active during engine operation?

Yes

- Replace the Powertrain Control Module in accordance with the Service Information.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- The problem may have been corrected when the harness connections were re-connected. Be certain that the PCM and chassis grounds are in good condition.
- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test