Circuit Description
The camshaft position (CMP) sensor is a magnetic generator type sensor that produces an alternating current signal. The CMP sensor signal increases in frequency as the engine RPM increases. The camshaft position signal is used by the PCM to determine optimum ignition timing and fuel delivery as well as misfire diagnosis. The engine will start and run without the CMP sensor signal.
Conditions for Setting the DTC
No CMP sensor signal to the PCM while cranking.
OR
No CMP sensor signal to PCM with engine speed at 600 RPM or more.
Action Taken When the DTC Sets
| • | The PCM illuminates the MIL. |
| • | The PCM stores the conditions which were present when the DTC set as Freeze Frame Data. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present. |
| • | The DTC clears after 40 consecutive warm-up cycles have occurred without a fault. |
| • | A DTC can be cleared by using the scan tool Clear DTC Information function. |
Diagnostic Aids
Check for any of the following conditions:
| • | The camshaft position (CMP) sensor output may be affected by temperature. Check the sensor's operation and internal resistance at various temperatures. The CMP sensor resistance when COLD should be between 835 ohms and 1,400 ohms at -10° to 50°C (14°-122°F). The CMP sensor resistance when HOT should be between 1,060 ohms and 1,645 ohms at 50°-100°C (122°-212°F). |
| • | CMP sensor performance can be checked with a DMM and a scan tool. The AC voltage output of the CMP sensor, as measured with a DMM across the sensor electrical terminals, is approximately the same as engine speed. Run the engine at several different engine speeds and compare the numerical value on the scan tool with the numerical voltage reading on the DMM. If the reading of the DMM and the scan tool are not nearly equal, check for a faulty sensor or signal rotor. |
| • | A DTC P0340 that sets while driving and checks OK may be caused by inadequate CMP sensor circuit shielding. Check that the CMP sensor circuit is properly shielded and that the drain wire is fastened securely to ground. |
An intermittent malfunction may be caused by a fault in the CMP sensor electrical circuit. Inspect the wiring harness and components for any of the following conditions:
| • | Backed out terminals. |
| • | Improper mating of terminals. |
| • | Broken electrical connectors locks. |
| • | Improperly formed or damaged terminals |
| • | Faulty terminal to wire connections. |
| • | Physical damage to the wiring harness. |
| • | A broken wire inside the insulation. |
| • | Corrosion of electrical connections, splices, or terminals. |
Repair any electrical circuit faults that were found. Refer to Wiring Repairs in Wiring Systems.
The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.
Test Description
The numbers below refer to the step numbers in the Diagnostic Table.
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The OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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This step checks for an open in the ground circuit of the CMP sensor from PCM terminal C1-17 to splice S209. The engine will not stay running, and a DTC P0340 will set, if the CMP sensor -- and CKP sensor -- ground circuit is open.
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This step checks whether DTC P0340 is the result of a hard failure or an intermittent condition.
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This step is checking the internal resistance of the camshaft position sensor. A typical value at 23°C (74°F) is 1.1k ohms.
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This step checks the CMP sensor output signal. The CMP sensor sends the PCM one electrical pulse (signal) for every revolution of the intake camshaft. Therefore the AC signal generated by the CMP sensor will be numerically analogous to the engine speed. With the engine speed at about 3,000 RPM, the CMP sensor voltage should be around 2.950-3.050 volts AC.
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This step checks the CKP input circuit to the PCM. The AC signal generated by the CMP sensor will be numerically analogous to the engine speed. With the engine speed at about 3,000 RPM, the CMP sensor voltage should be around 2.950-3.050 volts AC. The CMP sensor signal wire must be removed from the PCM connector in order to accurately check the sensor output. If the CMP sensor signal (input) wire is backprobed while connected to the PCM, the AC voltage indicated on a DMM will be approximately 15% to 20% lower than actual engine speed.
-
This step checks for a faulty signal rotor on the camshaft. Visually inspect the tooth of the signal rotor through the CMP sensor aperture for damage, foreign material, and installation.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||||||||
Does the vehicle not start or almost start and then stall immediately? | -- | |||||||||
Does the vehicle start and run with the MIL illuminated and a DTC P0340 set? | -- | |||||||||
4 |
Did a DTC P0340 set? | -- | Go to Diagnostic Aids | |||||||
Is the CMP sensor resistance within the specified value? | 835-1,400 ohms at -10° to 50°C (14°-122°F) or 1,060-1,645 ohms at 50°-100°C (122°-212°F) | |||||||||
Was the AC voltage indicated approximately equal to the engine speed? | -- | |||||||||
7 | Probe the ground circuit of the CMP sensor (harness side) with a test lamp connected to B+. Did the test lamp illuminate? | -- | ||||||||
Was the AC voltage indicated approximately equal to the engine speed? | -- | |||||||||
9 | Repair the open or the short in the CMP input circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
10 | Repair the open in the CMP and CKP sensors ground circuit between splice S209 and the PCM. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
11 | Repair the open in the CMP sensor ground circuit between the sensor and splice S209. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
Was a repair necessary? | -- | |||||||||
13 | Replace the CMP sensor. Refer to Camshaft Position Sensor Replacement . Is the action complete? | -- | -- | |||||||
14 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |||||||
15 |
Are any DTCs displayed on scan tool? | -- | Go to the applicable DTC table | System OK |
