P0338

DTC P0338 - CRANKSHAFT POSITION (CKP) SENSOR CIRCUIT HIGH DUTY CYCLE

CIRCUIT DESCRIPTION
The crankshaft position (CKP) sensor is located on the rear of bank 1 of the engine block. The CKP sensor produces an AC voltage of different amplitude and frequency depending on the velocity of the crankshaft. The CKP sensor works in conjunction with a 58X reluctor wheel that is attached to the crankshaft. Each tooth on the reluctor wheel are spaced 6 degrees apart with one span having a 12 degree space. The engine control module (ECM) uses the 12 degree space to determine top dead center for cylinders 1 and 4. The ECM determines when cylinder 1 is on the compression stroke by monitoring the CKP sensor and the camshaft position (CMP) sensors. The ECM can synchronize the ignition timing, fuel injector timing, and spark knock control based on the CKP sensor and the CMP sensor inputs. If the ECM detects more or less than 58 reference pulses within a certain number of crankshaft revolutions when the engine is cranking or operating, this DTC sets.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P0338 Crankshaft Position (CKP) Sensor Circuit High Duty Cycle

CONDITIONS FOR RUNNING THE DTC
- The engine is cranking or operating.
- The ECM has detected more than 12 camshaft revolutions.
- DTC P0338 runs continuously once the above conditions are met.

CONDITIONS FOR SETTING THE DTC
- The ECM detects a difference of more than 8 teeth between reference gap position pulses for 4 consecutive crankshaft revolutions in which the same number of pulses are detected each crankshaft revolution.
- The condition exists for more than 4 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
- The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.

DIAGNOSTIC AIDS
- Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector. Using this kit prevents damage to the harness or component terminals.
- The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to Engine Controls Component Views.
- The ECM uses the camshaft position sensors to determine engine speed and position when there is a CKP sensor condition.
- The engine will operate with a CKP sensor condition only if the ECM has stored the learned reference position of the camshafts in memory. With a crankshaft position sensor condition the engine will go into a limp home mode after a hard restart. The ECM then calculates engine speed from one of the camshaft position sensors. During a limp home mode the following additional DTCs may set and should be ignored:
- DTC P0324 Knock Sensor (KS) Module Performance
- DTC P1011 Intake Camshaft Position Actuator Park Position Bank 1
- The following conditions may cause this DTC to set:
- An intermittent condition in the CMP sensor circuits can cause a CKP DTC to set. Inspect the CMP sensor, harness connections, and related wiring, if you suspect this condition.
- Intermittent short to ground in the signal circuit
- Excessive air gap between the CKP sensor and the reluctor wheel
- CKP sensor damage or improper installation
- Crankshaft reluctor wheel damage or improper installation
- Foreign material passing between the CKP sensor and the reluctor wheel
- Excess crankshaft end play causes the reluctor wheel to move out of alignment with the CKP sensor. This could result in any one of the following conditions:
- A hard start
- A start and stall
- Erratic performance
- For an intermittent, refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION

Step 1 - Step 7:

Step 8 - Step 18:

Step 19 - Step 20:

The numbers below refer to the step numbers on the diagnostic table.
5. This step is testing for a poor connection at the components and for an intermittent condition with the wiring. Clearing the DTCs allows the ECM to synchronize the cam and crank reference pulses.
6. This step is testing for electromagnetic interference (EMI). If the CKP sensor circuits are routed close to high load circuits or components, this DTC may set.
7. This step is testing if the CKP sensor is installed correctly. A CKP sensor that is not fully seated, may cause this DTC to set.
8. This step is testing for an ECM condition. The ECM uses a pull-up voltage of 2.5 volts on each CKP sensor circuit to reduce noise interference from EMI. If the voltage is not present, replace the ECM.
9. This step is testing for an ECM condition. The ECM uses a pull-up voltage of 2.5 volts on each CKP sensor circuit to reduce noise interference from EMI. If the voltage is not present, replace the ECM.
10. This step tests for a condition in the CKP sensor ground shield. Normal EMI could effect the out-put signal of the CKP sensor if the shield is shorted to the other circuits of the CKP sensor, or grounded externally of the ECM.
12. Missing, damaged, or broken teeth on the reluctor wheel can set this DTC. If the crankshaft was recently replaced or the vehicle/engine is new and this DTC is set, inspect all teeth on the reluctor wheel.