Schematic Reference: Engine Controls Schematics
Circuit Description
The camshaft position (CMP) sensor is located in the distributor and consists of a signal generator (a hall element and magnet) and a signal rotor. As the signal rotor turns, a magnetic flux from the magnet is applied to the hall element repeatedly. The hall element generates a voltage that is proportional to the magnetic flux. This voltage signal is wave-shaped and is modified into a digital pulse by the comparator and sent to the engine control module (ECM). The ECM uses this 4 pulse/revolution signal to determine the engine speed and the position of each cylinder. The ECM uses this signal to control the fuel injectors and the ignition timing.
Conditions for Setting the DTC
No signal from the CMP sensor for 3 seconds with the ECM receiving an engine start signal.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn off after three consecutive drive cycles without a fault present. |
| • | A DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | The DTCs can be cleared by using a scan tool or by disconnecting the ECM battery feed. |
Diagnostic Aids
Check for any of the following conditions:
| • | If a DTC P1500 Starter Signal Circuit is set, diagnose P1500 first. |
| • | If no problem is found with the CMP sensor or the circuitry, check the CMP sensor signal rotor for proper alignment or damage. |
An intermittent malfunction may be caused by a fault in the CMP sensor circuit. Inspect the wiring harness and components for any of the following conditions:
| • | Backed out terminals. |
| • | Improper mating of terminals. |
| • | Broken electrical connector 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. |
If the DTC P0340 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions since the DTC was first set.
Test Description
The numbers below refer to the step numbers in the Diagnostic Table.
-
The Powertrain (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.
-
Determine if a fault is present. Review the Freeze Frame data to determine when the DTC set. Always record this information.
-
Line up one of the signal rotors with the hall element by turning the crankshaft until one of the rotors are in the proper position.
-
Move the crankshaft just enough so that the signal rotor is not in line with the hall element.
-
The CMP sensor is not serviced separately. Refer to distributor service in Engine Electrical for CMP sensor replacement.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Does the scan tool indicate a DTC P0340? | -- | Go to Diagnostic Aids | ||
3 |
Is the voltage at the specified value? | B+ | ||
4 | Probe the distributor connector terminal 1 (harness side) with a test lamp connected to B+. Did the test lamp illuminate? | -- | ||
Is the voltage between the specified value? | 3 to 5 volts | |||
Is the voltage between the specified value? | 0 to 1 volt | |||
7 | Repair the open in the CMP ignition feed circuit between the CMP sensor and the main relay. Repair as necessary. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
8 | Repair the open in the CMP ground circuit or faulty ground connection. Repair as necessary. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
9 |
Was a repair necessary? | -- | ||
Replace the CMP sensor. Refer to Camshaft Position Sensor Replacement. Is the action complete? | -- | -- | ||
11 | Replace the ECM. Refer to Engine Control Module Replacement. Is the action complete? | -- | -- | |
12 |
Are any DTCs displayed on the scan tool? | -- | Go to the Applicable DTC Table | System OK |
