Circuit Description
The camshaft position (CMP) sensor is a 1X sensor. The CMP provides one digital ON/OFF signal to the powertrain control module (PCM) per revolution of the camshaft. This information is used by the PCM to determine the position of the valve train relative to the crankshaft position (CKP). By monitoring the CMP and CKP signals, the PCM can accurately time the operation of the fuel injectors. The CMP sensor is connected directly to the ignition control module (ICM). The sensor wiring includes the following circuits which are shared with the CKP sensor:
| • | The CMP sensor signal circuit |
| • | A 12-volt reference circuit |
| • | A low reference circuit |
The signal is passed through the ICM to the PCM on the camshaft position signal circuit. The PCM monitors the CMP sensor for errors. If the PCM does not receive a signal from the CMP sensor, DTC P0340 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0340 Camshaft Position (CMP) Sensor Circuit
Conditions for Running the DTC
| • | The engine is cranking. |
| OR |
| • | The engine is running for more than 3 seconds. |
| • | This diagnostic runs continuously when either condition is met. |
Conditions for Setting the DTC
| • | The PCM detects the following for every 2 engine revolutions: |
| - | 36 medium resolution engine speed signals |
| - | 6 low resolution engine speed signals |
| - | 0 camshaft position signals |
| • | 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 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
Inspect for the following conditions:
| • | Any secondary ignition wires arcing to a wiring harness and for carbon tracking or other signs of damage |
| • | A faulty ignition coil |
| • | The ignition control module and the coils for cracks, carbon tracking, or other signs that indicate that the coil secondary circuit is arcing to the ICM or to the ICM wiring harness--Refer to Ignition Coil Replacement . |
If the condition is suspected of being intermittent, refer to Testing for Intermittent Conditions and Poor Connections .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This test verifies if the sensor is working correctly. By suppling a ground to the circuit, the voltage should change when the circuit is touched with a test lamp.
-
This step determines if the fault is caused by a missing camshaft magnet or by a faulty PCM. The voltage measured in this step should be near 5 volts, and decrease to near 0 volts when the CMP sensor interfaces with the camshaft magnet.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 | Attempt to start the engine. Does the engine start and run? | -- | Go to Step 3 | Go to Step 4 |
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids |
4 |
Important: If voltage measures 0 volts, rotate the crankshaft to ensure the camshaft position (CMP) sensor magnet is not located under the CMP sensor at the time of the test. Is the voltage within the specified range? | 4.5-5.5 V | Go to Step 8 | Go to Step 5 |
5 | Does the voltage on the CMP signal circuit measure more than the specified value? | 5 V | Go to Step 16 | Go to Step 6 |
6 | Probe the CMP signal circuit at the PCM connector with a test lamp that is connected to battery voltage. Refer to Probing Electrical Connectors . Does the test lamp illuminate? | -- | Go to Step 15 | Go to Step 7 |
7 |
Is the resistance within the specified value? | 0-5 ohms | Go to Step 8 | Go to Step 14 |
8 |
Important: The magnet used must have sufficient power and the correct polarity. If the voltage remains at 5 volts, retest using the opposite end of the magnet. Does the voltage toggle from 5 volts to 0 volts when the magnet is moved across the sensor surface? | -- | Go to Step 24 | Go to Step 9 |
9 |
Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 17 |
10 |
Is the resistance within the specified value? | 0-5 ohms | Go to Step 11 | Go to Step 18 |
11 |
Is the voltage within the specified Range? | 4-8 V | Go to Step 12 | Go to Step 21 |
12 |
Is the resistance within the specified range? | 0-5 ohms | Go to Step 13 | Go to Step 19 |
Does the voltage change when the circuit is touched? | -- | Go to Step 23 | Go to Step 22 | |
14 | Repair the open in the CMP signal circuit between the ICM and the PCM. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 30 | -- |
15 | Test the CMP signal circuit between the ICM and the PCM for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 30 | Go to Step 22 |
16 | Test the CMP signal circuit between the ICM and the PCM for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 30 | Go to Step 22 |
17 | Test the CMP 12-volt reference circuit between the CMP sensor and the ICM for an open, high resistance, or a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 30 | Go to Step 22 |
18 | Repair the open or high resistance in the low reference circuit between the CMP sensor and the ICM. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 30 | -- |
19 | Test for an open or high resistance in the CMP sensor signal circuit between the CMP sensor and the ICM. Refer to Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 30 | Go to Step 21 |
20 | Test the CMP sensor signal circuit between the CMP sensor and the ICM for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 30 | Go to Step 22 |
21 | Test the CMP sensor signal circuit between the CMP sensor and the ICM for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 30 | Go to Step 22 |
22 | Test for an intermittent and for a poor connection at the ICM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 30 | Go to Step 26 |
23 | Test for an intermittent and for a poor connection at the CMP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 30 | Go to Step 27 |
24 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 30 | Go to Step 25 |
Does the voltage toggle from 5 volts to 0 volts while bumping the engine with the starter? | -- | Go to Step 28 | Go to Step 29 | |
26 | Replace the ICM. Refer to Ignition Control Module Replacement . Did you complete the replacement? | -- | Go to Step 30 | -- |
27 | Replace the CMP sensor. Refer to Camshaft Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 30 | -- |
28 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 30 | -- |
29 | Replace a faulty or missing CMP sensor magnet on the camshaft sprocket. Did you complete the replacement? | -- | Go to Step 30 | -- |
30 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 31 |
31 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
