Circuit Description
This ignition system does not use a conventional camshaft position (CMP) sensor that detects valve train position. The ignition control module (ICM) detects when #1 or #3 cylinder has fired on its compression stroke using sensing circuitry integrated within each coil. The sensing circuit detects the polarity and the strength of the secondary voltage output, the higher output is always at the event cylinder. The ICM sends a CMP signal to the powertrain control module (PCM) based on the voltage difference between the event and waste cylinder firing energy. This system is called compression sense ignition. By monitoring the CMP and crankshaft position (CKP) signals, the PCM can accurately time the operation of the fuel injectors. If the PCM receives an intermittent CMP signal from the ICM, the CMP Resync Counter on the scan tool will increment. When the PCM cannot use the information from the CMP signal, DTC P0340 will set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0340 Camshaft Position (CMP) Sensor Circuit
Conditions for Running the DTC
| • | The engine is running. |
| • | The manifold absolute pressure (MAP) is more than 55 kpa. |
| • | DTC P0340 runs continuously once the engine is running. |
Conditions for Setting the DTC
The PCM does not detect any change in the CMP signal for more than 6 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 3 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
| • | The following conditions may cause this DTC to set: |
| - | Low resistance in both the #1 and #3 secondary ignition circuits |
| - | High resistance in both the #4 and #2 secondary ignition circuits |
| - | An intermittent Crank Signal |
| • | An Intermittent crank signal will result in an interrupted cam signal and may set this DTC. |
| • | To locate an intermittent problem, use the scan tool to monitor CMP Active Counter parameter while running the engine. The counter should continuously count up to 255, then reset to zero. The counter will stop counting if a fault occurs in the cam signal circuit. |
| • | If this DTC is determined to be intermittent, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step determines if the ignition system is working correctly .
-
This step determines if the interconnect is bad or if a poor connection exists between the ICM and the Coil Cassette.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connect End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||
2 |
Does the scan tool indicate the CMP active counter is incrementing? | -- | Go to Step 3 | Go to Step 4 | ||||||||
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids | ||||||||
Is the duty cycle within the specified range? | 45-55% | Go to Step 6 | Go to Step 5 | |||||||||
Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 7 | |||||||||
6 | Test the CMP signal circuit for the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 8 | ||||||||
7 | Test for an intermittent and for a poor connection at the ICM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 9 | ||||||||
8 | Test for an intermittent and for a poor connection at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 10 | ||||||||
9 | Replace the ICM. Refer to Ignition Control Module Replacement . Did you complete the replacement? | -- | Go to Step 11 | -- | ||||||||
10 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 11 | -- | ||||||||
11 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 12 | ||||||||
12 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK | ||||||||
