MIL ON - DTC P0340/P0341, Cam Sensor Circuit
BULLETIN NO.: 98-T-49AISSUE DATE: August, 1999
GROUP/SEQ. NO.: Engine-08
CORPORATION NO.: 99-06-04-033
SUBJECT:
(MIL) SERVICE ENGINE SOON Telltale On with Diagnostic Trouble
Codes (DTCs) P0340 and/or P0341, Cam Sensor Circuit Performance
(Diagnose and Repair as Necessary using Updated Diagnostic
Information Contained in this Bulletin)
This bulletin has been revised to incorporate the ignition coil assembly (P/N 16167763) as a service part and supercedes bulletin 98-T-49, which should be discarded.
MODELS AFFECTED:
1996-1998 Saturn S-Series vehicles
CONDITION:
Vehicle may experience the (MIL) SERVICE ENGINE SOON telltale On with DTCs P0340 and/or P0341.
CAUSE:
DTCs P0340 and P0341 may be caused by incorrect resistance in the secondary ignition system. This incorrect resistance can cause the EI Module to incorrectly signal the cam position to the PCM.
CORRECTION:
The diagnostic information for DTCs P0340 and P0341 has been updated to include inspection of various secondary ignition components.
Refer to the diagnostic charts within this bulletin for further diagnostic information.
CMP SENSOR CIRCUIT PERFORMANCE (Chart 1 of 2)
For complete description of circuit operation, refer to Circuit Description in this bulletin.
DIAGNOSTIC AIDS
IMPORTANT:
A cam pulse signal error may not effect engine operation.
^ Inspect EI module coil towers and plug wire connections for corrosion or other signs of poor retention at connections.
^ Wire resistance 1.5K to 15K ohms.
^ Wire positioning on coils 4-1-2-3.
^ Coil pack secondary resistance (tower-to-tower) 8K-15K ohms
^ Spark plug gap 1.0 mm (.040 in.)
^ Check connector at EI Module using gray male adapter (from connector test adapter kit J-35616A) to ensure a good mechanical connection at terminal D, circuit 633. Repair if needed.
Notes on Diagnostic Chart 1:
CMP SENSOR CIRCUIT PERFORMANCE (Chart 2 of 2)
For complete description of circuit operation, refer to Circuit Description in this bulletin.
DIAGNOSTIC MDS
IMPORTANT:
A cam pulse signal error may not effect engine operation.
^ Inspect EI module coil towers and plug wire connections for corrosion or other signs of poor retention at connections.
^ Wire resistance 1.5K to 15K ohms.
^ Wire positioning on coils 4-1-2-3.
^ Coil pack secondary resistance (tower-to-tower) 8K-15K ohms
^ Spark plug gap 1.0 mm (.040 in.)
^ Check connector at EI Module using gray male adapter (from connector test adapter kit J-35616A) to ensure a good mechanical connection at terminal D, circuit 633. Repair if needed.
Notes on Diagnostic Chart 2:
CIRCUIT DESCRIPTION
The cam signal is a 5 volt signal (circuit 633) that is pulled to ground to inform the PCM that # 4 cylinder has fired on compression. A much higher voltage is needed to fire a cylinder that is on the compression stroke. The EI module monitors this firing voltage on the # 1-4 coil to determine if cylinder # 1 or cylinder # 4 is firing. This signal, along with the double pulse received from the CKP sensor synchronizes fuel timing.
Under normal operation, the 7X (CMP RESYNC) COUNTER continuously counts the notches in the crankshaft as it rotates, and resets to zero each time the CMP sensor detects the # 4 cylinder firing. Therefore, the 7X (CMP RESYNC) COUNTER should continuously count from 0 to 14 with each two crankshaft revolutions. If the cam signal is missing, the 7X COUNTER will count to 255 and stay fixed and a P0340 will set. If the cam signal is present too often, the counter will not reach 14 and a P0341 will set.
If the ignition secondary (coil, pair of spark plugs and wires) has incorrect resistance, open or corrosion in the circuit that influences firing voltage, the EI module can incorrectly interpret these voltages and cause codes P0340 and/or P0341 to set.
PROCEDURES
1. Remove corrosion from EI module coil tower terminals using a 3M(R) Scotch-Brite fiber pad or equivalent. Do not use any solvents or cleaners to aid in corrosion removal. Do not contact or scratch the plastic sealing surfaces below the terminal. If the coil tower terminals are damaged by corrosion or pitting, replace coil.
2. Replace corroded spark plug wire(s) with new service spark plug wires. Add a liberal amount of dielectric grease to the coil tower terminals before installing new spark plug wires.
3. Test to ensure a positive "click" noise is heard when seating the spark plug wire on the terminal. If a positive seating and "click" noise is not obtained after cleaning, replace the affected coil.
PARTS REQUIREMENTS:
IMPORTANT:
On 1996 vehicles, if spark plugs are replaced, and vehicle was equipped with 0.060 in. gap plugs, all four spark plugs and the "Vehicle Emissions Control Information Label" must be replaced. Refer to Technical Information Bulletin 96-T-25, "Engine Cranks but will not Start, or Engine Stalls Immediately After Start Followed by Extended Cranking, and/or Ignition Misfire Resulting in DTCs P0300, P0301, P0302, P0303, P0304."
CLAIM INFORMATION:
To receive credit for this repair during the warranty coverage period, submit a claim through the Saturn Dealer System for one of the following depending on repair performed: