P2579

P2579-TURBOCHARGER SPEED SENSOR CIRCUIT PERFORMANCE







For a complete wiring diagram Refer to Diagrams/Electrical.

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 Engine Control Module (ECM) 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 Engine Control Module (ECM) 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.

Possible Causes:

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


1. DTC ACTIVE



NOTE: If there are any DTCs present for the Boost Pressure Sensor, perform the diagnostic procedure for those DTCs before continuing with this test.

1. Use the accelerator pedal to accelerate the engine speed to a high idle (100%) and hold the engine speed at high idle for at least 20 seconds.



Does P2579 become active?


Yes


- Go To 2



No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test



2. 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 3

No

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



3. (K540) TURBO SPEED SIGNAL CIRCUIT SHORTED TO GROUND







1. Disconnect the ECM C1 harness connector.
2. Measure the resistance between ground and the (K540) Turbo Speed Sensor Signal circuit in at the ECM C1 harness connector.



Is the resistance below 10k Ohms?


Yes

- Repair the short to ground in the (K540) Turbo Speed Sensor Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test


No


- Go To 4


4. (K540) TURBO SPEED SENSOR SIGNAL CIRCUIT SHORTED TO THE (K541) TURBO SPEED SENSOR GROUND CIRCUIT







1. Measure the resistance between the (K540) Turbo Speed Sensor Signal circuit and (K541) Turbo Speed Sensor Ground circuit at the ECM C1 harness connector.



Is the resistance below 10.0 Ohms?


Yes


- Repair the short between the (K540) Turbo Speed Sensor Signal circuit and (K541) Turbo Speed Sensor Ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 5


5. (K540) TURBO SPEED SENSOR SIGNAL CIRCUIT OPEN/HIGH RESISTANCE







1. Measure the resistance of the (K540) Turbo Speed Sensor Signal circuit between the Turbo Speed Sensor harness connector and the ECM C1 harness connector.

Is the resistance below 10.0 Ohms?


Yes

- Go To 6

No

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


6. ENGINE CONTROL MODULE (ECM)

1. Reconnect the ECM C1 harness connector.
2. Start the engine.
3. Use the accelerator pedal to accelerate the engine speed to a high idle (100%) and hold the engine speed at high idle for at least 20 seconds.


Does DTC P2579 become active during engine operation?


Yes

- Replace the Engine Control Module (ECM) in accordance with the Service Information.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test


No

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