Page 1 of 7 2002 Buick Regal Century, Regal (VIN W) Service Manual Engine Document ID: 861441 #02-06-04-008: SMU - Revised DTC P0341 Camshaft Position (CMP) Sensor Performance - (Feb 20, 2002) Subject: Revised DTC P0341 Camshaft Position (CMP) Sensor Performance Models: 2002 Buick Park Avenue, Regal 2002 Chevrolet Camaro 2002 Pontiac Firebird, Grand Prix with 3.8L Engine (VIN K - RPO L36) This bulletin is being issued to revise DTC P0341 Camshaft Position (CMP) Sensor Performance in the Engine Controls-3.8L sub-section of the Service Manual. Please replace the current information in the Service Manual with the following information. This revised DTC requires a different diagnostic approach due to a change that affects diagnosis of the camshaft position (CMP) sensor circuit. The change affects the CMP circuit by possibly causing an "engine cranks but does not run" condition if the powertrain control module (PCM) does not recognize the CMP sensor signal. The PCM may or may not set DTC P0341 depending on if the engine was running at the time of the failure. The following information has been updated within SI2000. If you are using a paper version of this Service Manual, please make a reference to this bulletin on the affected page. Circuit Description The camshaft position (CMP) sensor is a hall-effect type sensor. The sensor produces one signal for each revolution of the camshaft in order to control the sequential fuel injection. There are no direct circuits from the CMP sensor to the powertrain control module (PCM). All of the circuits are between the CMP sensor and the ignition control module (ICM). These circuits are the CMP signal circuit, the 12-volt reference circuit, and the low reference circuit. The ICM also supplies a camshaft position signal circuit to the PCM. The PCM compares the CMP sensor signal to the number of 3X, low-resolution, engine speed signals generated by the ICM. The normal ratio of 3X signals is 6 to 1. If the PCM receives an incorrect number of CMP sensor signals, this DTC sets. Conditions for Running the DTC The engine is running and 3X reference pulses are being received. Conditions for Setting the DTC The PCM does not receive CMP sensor reference pulses during one rotation of the camshaft. Diagnostic Aids Inspect for the following conditions: 2008 General Motors Corporation. All rights reserved.
Page 2 of 7 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(s) Replacement. If the condition is suspected of being intermittent, refer to Intermittent Conditions. Test Description The numbers below refer to the step numbers on the diagnostic table. 14. This test verifies if the sensor is working correctly. By supplying a ground to the circuit, the voltage should change when touched with the test lamp. 26. 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. DTC P0341 Step Action Values Yes No Schematic Reference: Engine Controls Schematics 1 2 3 4 Did you perform the Diagnostic System Check-Engine Controls? Attempt to start the engine. Does the engine start and run? 1. Turn Off the ignition for 30 seconds. 2. Start the engine. 3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? 2. Disconnect the powertrain control module (PCM). 3. Turn ON the ignition, with the engine Important: If voltage measures 0 volts, bump over the engine in order to ensure the CMP sensor magnet is not located under the camshaft position (CMP) sensor at the time of the test. 4.5-5.5 V Go to Step 2 Go to Diagnostic System Check Engine Controls Go to Step 3 Go to Step 4 Go to Step 4 Go to Diagnostic Aids
Page 3 of 7 4. Measure the voltage from the camshaft connector to a good ground with a DMM. Refer to Circuit Testing in Wiring Is the voltage within the specified range? Go to Step 8 Go to Step 5 5 Does the voltage on the camshaft position signal circuit measure more than the specified value? 5 V Go to Step 17 Go to Step 6 6 Probe the camshaft position signal circuit at the PCM connector with a test lamp that is connected to battery voltage. Refer to Probing Electrical Connectors in Does the test lamp illuminate? Go to Step 16 Go to Step 7 7 1. Disconnect the ICM. 2. Measure the resistance of the camshaft position signal circuit between the ignition control module (ICM) and the PCM with a DMM. Refer to Circuit Testing in 05Ω Is the resistance within the specified value? Go to Step 8 Go to Step 15 2. Remove the CMP sensor from the engine front cover without disconnecting the CMP sensor harness connector. Refer to Camshaft Position (CMP) Sensor Replacement. 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. 3. Turn ON the ignition, with the engine 4. Place a magnet on the CMP sensor. 5. Measure the voltage from the camshaft connector to a good ground with a DMM. Refer to Circuit Testing in Wiring Does the voltage toggle from 5 volts to 0 volts when the magnet is placed on the sensor? Go to Step 25 Go to Step 9 2. Install the CMP sensor to the engine front cover. 3. Disconnect the CMP sensor.
Page 4 of 7 9 10 11 12 13 4. Turn ON the ignition with the engine 5. Probe the 12-volt reference circuit of the CMP sensor with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors in Wiring Does the test lamp illuminate? 1. Turn OFF the ignition 2. Disconnect the ICM. 3. Measure the resistance of the low reference circuit of the CMP sensor from the CMP connector to the ICM connector with a DMM. Refer to Circuit Testing in Is the resistance within the specified value? 1. Connect the ICM. 2. Turn ON the ignition, with the engine 3. Measure the voltage from the CMP sensor signal circuit of the CMP sensor to a good ground with a DMM. Refer to Circuit Testing in Is the voltage less than the specified value? 2. Disconnect the ICM. 3. Measure the resistance of the CMP sensor signal circuit from the CMP sensor connector to the ICM connector with a DMM. Refer to Circuit Testing in Is the resistance within the specified range? 1. Connect the ICM. 2. Turn ON the ignition, with the engine 3. Probe the CMP sensor signal circuit of the CMP sensor with a test lamp that is connected to battery voltage. Refer to Probing Electrical Connectors in Wiring Does the test lamp illuminate? 1. Connect the ICM. 2. Disconnect the PCM. 3. Turn ON the ignition, with the engine 4. Momentarily and repeatedly probe the CMP sensor signal circuit with a test 0-5Ω 7 V 0-5Ω Go to Step 10 Go to Step 18 Go to Step 11 Go to Step 19 Go to Step 12 Go to Step 22 Go to Step 13 Go to Step 20 Go to Step 21 Go to Step 14
Page 5 of 7 14 lamp that is connected to a good ground. 5. Measure the voltage on the camshaft connector to a good ground with a DMM. Refer to Circuit Testing in Wiring 15 16 17 18 19 20 21 Does the voltage change when the circuit is touched? Repair the camshaft position signal circuit between the ICM and the PCM for an open. Refer to Wiring Repairs in Did you complete the repair? Test the camshaft position signal circuit between the ICM and the PCM for a short to ground. Refer to Circuit Testing and Wiring Repairs n Test the camshaft position signal circuit between the ICM and the PCM for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Test the CMP 12-volt reference circuit between the CMP sensor and the ICM for an open, a high resistance, or a short to ground. Refer to Circuit Testing and Wiring Repairs in Repair the CMP low reference circuit between the CMP sensor and the ICM for an open or high resistance. Refer to Wiring Repairs in Did you complete the repair? Repair the CMP sensor signal circuit between the CMP sensor and the ICM for an open or high resistance. Refer to Wiring Repairs in Did you complete the repair? 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 in Go to Step 24 Go to Step 23 Go to Step 31 Go to Step 31 Go to Step 31
Page 6 of 7 22 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 in 23 24 25 26 27 28 29 Test for an intermittent and for a poor connection at the ICM. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Test for an intermittent and for a poor connection at the CMP sensor. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in 1. Install the CMP sensor to the engine front cover. Refer to Camshaft Position (CMP) Sensor Replacement. 2. Measure the voltage of the camshaft connector to ground with a DMM. Refer to Circuit Testing in 3. Observe the voltage while repeatedly bumping the engine with the starter. Does the voltage toggle from 5 volts to 0 volts while bumping the engine with the starter. Replace the ICM. Refer to Ignition Control Module Replacement. Replace the CMP sensor. Refer to Camshaft Position (CMP) Sensor Replacement. Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement. Go to Step 31 Go to Step 27 Go to Step 31 Go to Step 28 Go to Step 31 Go to Step 26 Go to Step 29 Go to Step 30 Go to Step 31 Go to Step 31 Go to Step 31 Replace a faulty or missing CMP sensor
Page 7 of 7 30 magnet on the camshaft sprocket. Go to Step 31 31 1. Clear the DTC's with a scan tool. 2. Turn OFF the ignition for 30 seconds. 3. Start the engine. 4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? Go to Step 2 Go to Step 32 32 Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? Go to Diagnostic Trouble Code (DTC) List System OK GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information. WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION