DTC P0343 Camshaft Position (CMP) Sensor Circuit High Voltage. GMC Truck GMC C-Series Medium Duty Truck C6/C7/C8 1999

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC C-Series Medium Duty Truck C6/C7/C8 🢒 DTC 🢒 DTC P0343 Camshaft Position (CMP) Sensor Circuit High Voltage

Engine Controls Components
Cell 20: Camshaft Position Sensor, Crankshaft Position Sensor
Handling ESD Sensitive Parts Notice

Circuit Description

The Camshaft Position sensor is mounted through the top of the engine block at the rear of the engine. Camshaft Position Sensor (CKP Sensor), is splined by a helical gear to the camshaft and rotates providing a 1X signal (one pulse per camshaft revolution). The PCM provides a 12 volt power supply to the CMP sensor as well as a ground and a signal circuit.

The Camshaft Position sensor is used to determine whether a cylinder is on a firing or exhaust stroke. As the camshaft rotates, the reluctor wheel interrupts a magnetic field produced by a magnet within the sensor. The sensors internal circuitry detects this and produces a signal which is read by the PCM. The PCM uses this 1X signal in combination with the Crankshaft Position sensor 24X signal to determine crankshaft position and stroke. This diagnostic for the Camshaft Position sensor checks for a loss of Camshaft Position sensor signal.

Note that as long as the 24X signal is available, the engine can start even if there is no Camshaft Position sensor signal. The PCM can determine when a particular cylinder is on either a firing or exhaust stroke by the 24X signal alone, but requires the cam signal to determine which (firing or exhaust). The system will attempt synchronization and look for an increase in MAF signal indicating the engine started. If no MAF increase is detected, the PCM assumes it incorrectly synchronized to the exhaust stroke and will re-sync to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.

Conditions for Running the DTC

•	System voltage is between 9.0 volts and 17.0 volts.

•	Engine speed is less than 4000 RPM.

Conditions for Setting the DTC

The PCM detects the Cam signal is stuck high when the signal should be low for 1.5 seconds.

Action Taken When the DTC Sets

•	The PCM will illuminate the Malfunction Indicator Lamp (MIL) on the second consecutive drive trip that the diagnostic runs and fails.

•

The PCM will record operating conditions at the time the diagnostic fails. The first time the diagnostic fails, this information will be stored in Failure Records. If the diagnostic reports a failure on the second consecutive drive trip, the operating conditions at the time of failure will be written to Freeze Frame and the Failure record will be updated.

Conditions for Clearing the MIL/DTC

•	The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.

•	A last test failed (Current DTC) will clear when the diagnostic runs and does not fail.

•	A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

•	PCM battery voltage is interrupted.

•	Using a Scan tool.

Diagnostic Aids

The following mechanical problems may cause this DTC to set:

•	Poor connections/terminal tension at the sensor.

•	Camshaft reluctor wheel damage.

•	The sensor coming in contact with the reluctor wheel.

Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If the DTC cannot be duplicated, the information included in the Freeze Frame and/or Failure Records data can be useful in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also be used to determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that were noted. This will isolate when the DTC failed.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

This step verifies that the fault is present. A hard start is observed when a malfunction is present.

This step checks the Camshaft Position sensor B+ reference circuit from the PCM to the CMP.

This step checks the Camshaft Position sensor ground circuit from the PCM to the CMP.

This step checks the Camshaft Position sensor signal circuit. Applying a voltage causes the CAM signal input - High to Low and Low to High parameter to increase if the circuit and the PCM are operating properly.

This step checks the Camshaft Position sensor output. The sensor must have a voltage supply and a ground to perform this test. A duty cycle that is present, indicates the condition is intermittent. Inspect the harness connectors for poor connections.

This step checks the Camshaft Position sensor B+ reference circuit from the PCM to the CMP sensor.

This step checks the Camshaft Position sensor ground circuit from the PCM to the CMP sensor.

Step

Action

Value(s)

Yes

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Install a scan tool.
Idle the engine.
Monitor the CAM signal input - High to Low and Low to High transition parameter in the Engine Data List 1 using the scan tool.

Does the scan tool parameter increment?

Go to Step 3

Go to Step 4

Turn ON the ignition leaving the engine OFF.
Review the Freeze Frame and/or Failure Records data for this DTC and observe the parameters.
Turn OFF the ignition for 15 seconds.
Idle the engine.
Operate the vehicle within the conditions required for this diagnostic to run, and as close to the conditions recorded in Freeze Frame/Failure Records as possible. Special operating conditions that you need to meet before the PCM will run this diagnostic, where applicable, are listed in Conditions for Running the DTC.
Select the Diagnostic Trouble Code (DTC) option, the Specific DTC option, then enter the DTC number using the scan tool.

Does the scan tool indicate that this diagnostic failed this ignition?

Go to Step 4

Go to Diagnostic Aids

Turn OFF the ignition .
Disconnect the Camshaft Position Sensor (CMP).
Turn ON the ignition leaving the engine OFF.
Install the brown terminal from the terminal kit J 35616 .
Probe the Camshaft Position sensor ignition feed circuit (PCM harness side) with one lead of the DMM and connect the other lead to battery ground.

Does the DMM display near the specified value?

B+

Go to Step 5

Go to Step 8

Measure the voltage from the Camshaft Position sensor ignition feed circuit to the Camshaft Position sensor ground circuit using the DMM.

Does the DMM display near the specified voltage?

B+

Go to Step 6

Go to Step 10

Start the engine.
Monitor the CAM signal input - High to Low and Low to High transition in the Engine Data List 1 using the scan tool.
Momentarily and repeatedly probe the signal circuit with a fused jumper connected to B+.

Does the CAM signal input - High to Low and Low to High transition counters increment when the jumper contacts the signal circuit?

Go to Step 7

Go to Step 11

At the CMP sensor, Jumper the ignition feed and the ground circuit between the PCM side of the harness to the camshaft position sensor.
Connect a third jumper to the signal circuit of the camshaft position sensor.
Idle the engine.
Connect the DMM.
Set the DMM to DC voltage and to the duty cycle position.

Does the DMM display a percentage within the specified range?

45-55%

Go to Diagnostic Aids

Go to Step 18

Disconnect the PCM connector located on the opposite side of the manufacturer's logo. Refer to Powertrain Control Module Replacement/Programming .
Check the continuity of the CMP ignition feed circuit using the DMM.

Is there continuity?

Go to Step 9

Go to Step 13

Check the CMP ignition feed circuit for the following:

•	A grounded circuit

•	A poor connection

Did you find and correct the condition?

Go to Step 20

Go to Step 17

Disconnect the PCM connector located on the same side as the manufacturer's logo. Refer to Powertrain Control Module Replacement/Programming .
Check the continuity of the CMP ground circuit using the DMM.

Is there continuity?

Go to Step 17

Go to Step 14

Disconnect the PCM connector located on the same side as the manufacturer's logo. Refer to Powertrain Control Module Replacement/Programming .
Check the continuity of the CMP signal circuit using the DMM.

Is there continuity?

Go to Step 12

Go to Step 15

Check the CMP signal circuit for the following:

•	A grounded circuit

•	A circuit shorted to a voltage

Did you find and correct the condition?

Go to Step 20

Go to Step 16

Inspect the CMP ignition feed circuit for an open circuit.
If you find a circuit open, repair the CMP ignition feed circuit .

Did you find and correct the condition?

Go to Step 20

Go to Step 17

Repair the CMP ground circuit for an open. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 20

Repair the CMP signal circuit for an open. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 20

Inspect the connection at the CMP harness connector for proper connections.

Did you find and correct the condition?

Go to Step 20

Go to Step 18

Inspect the connection at the PCM harness connector for proper connections. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 20

Go to Step 19

Replace the Camshaft Position sensor. Refer to Camshaft Position Sensor Replacement .

Is the action complete?

Go to Step 20

Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming .

Is the action complete?

Go to Step 20

Select the Diagnostic Trouble Code (DTC) option and the Clear DTC Information option using the scan tool.
Idle the engine at the normal operating temperature.
Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, if applicable.

Does the scan tool indicate that this test ran and passed?

Go to Step 21

Go to Step 2

Select the Capture Info option and the Review Info option using the scan tool.

Does the scan tool display any DTCs that you have not diagnosed?

Go to applicable DTC Table

System OK