Mechanics

CHEVY CAMSHAFT/CRANKSHAFT SENSORS

1999 Chevrolet Silverado

Engine Performance problem
1999 Chevy Silverado 6 cyl Four Wheel Drive Automatic 113000 miles

Put on machine and came back with P1345 code. I checked the voltage input at the crank sensor and got 12 volts, output voltage was 2.5 volts.
Input voltage at the cam sensor was 12 volts, output voltage was steadily fluctuating up and down the scale from approx. 10 volts to 2.5 volts.
My question is whether this voltage is correct and there is no problem with the sensors, or are one or both faulty maybe.
Truck has had new plugs, wires, air filter and oil change but has like a misfire while driving about 75 % of the time any ideas?
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Rick7754
February 26, 2009.




DTC P1345 DTC P1345: CRANKSHAFT/CAMSHAFT POSITION SENSOR CORRELATION (4.3L, 5.0L, 5.7L & 7.4L " C", " G", " K" & " P" SERIES) Circuit Description This DTC monitors the CKP and CMP signals to determine if they are synchronized. If both signals are not observed by the VCM within a specified time, VCM will determine that error has occurred. DTC will set when engine is running, cam sensor reference pulse is not detected at correct relative position with crank pulse. Diagnostic Procedures 1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step. 2. Start engine. Using scan tool, monitor engine RPM. If engine RPM fluctuates up to twice the expected RPM, go to next step. If engine RPM does not fluctuate up to twice the expected RPM, go to step 4. 3. Replace crankshaft position sensor. After replacing sensor, go to step 10. 4. Start engine. Raise engine speed to 1000 RPM. Monitor camshaft retard on scan tool. If camshaft retard is -2 to 2 degrees, go to next step. If camshaft retard is not -2 to 2 degrees, go to step 6. 5. Increase engine speed to 2000 RPM. Check camshaft retard on scan tool. If camshaft retard changes more than 2 degrees of previous reading, go to next step. If camshaft retard does not change more than 2 degrees of previous reading, see DIAGNOSTIC AIDS. 6. Check for proper installation of distributor. Remove distributor cap and gently attempt to rotate rotor. If rotor turns on distributor shaft, go to step 9. If rotor does not turn on distributor shaft, go to next step. 7. Check for proper installation of distributor. Repair as necessary. After repairs, go to step 10. If distributor installation is okay, go to next step. 8. Perform Camshaft Retard Offset adjustment as follows: Turn engine off. Slightly loosen distributor hold-down bolt. Start and operate engine at 1000 RPM. Using scan tool, monitor camshaft retard offset. To compensate to a negative reading, rotate distributor counterclockwise. To compensate for positive reading, rotate distributor clockwise. Set offset to zero degrees, then tighten distributor hold-down bolt. If zero degrees is obtained, go to next step. If zero degrees cannot be obtained, see DIAGNOSTIC AIDS. 9. Replace distributor. After replacing distributor, go to next step. 10. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2. NOTE: For circuit reference, see appropriate wiring diagram in WIRING DIAGRAMS article.11. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTCs are displayed, go to applicable DTC test. DIAGNOSTIC AIDS Check for loose CMP sensor, excessive free play in timing chain and gear assembly, incorrectly installed distributor, loose rotor or distributor hold-down bolt. An intermittent may be caused by a poor connection, rubbed-through wire insulation or a broken wire inside insulation. Circuit Description This DTC monitors the CKP and CMP signals to determine if they are synchronized. If both signals are not observed by the VCM within a specified time, VCM will determine that error has occurred. DTC will set when engine is running, cam sensor reference pulse is not detected at correct relative position with crank pulse. Diagnostic Procedures 1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step. 2. Install scan tool. Start engine. Using scan tool, monitor engine RPM. If engine RPM fluctuates up to twice the expected RPM, go to next step. If engine RPM does not fluctuate up to twice the expected RPM, go to step 4. 3. Replace crankshaft position sensor. After replacing sensor, go to step 9. 4. Install scan tool. Start engine. Raise engine speed to 1000 RPM. Monitor camshaft retard on scan tool. If camshaft retard is -5 to -17 degrees, go to next step. If camshaft retard is not -5 to -17 degrees, go to step 6. 5. Raise engine speed to 2000 RPM. Check camshaft retard on scan tool. If camshaft retard changes more than 2 degrees of previous reading, go to next step. If camshaft retard does not change more than 2 degrees of previous reading, see DIAGNOSTIC AIDS. 6. Check for proper installation of distributor. Remove distributor cap and gently attempt to rotate rotor. If rotor turns on distributor shaft, go to step 8. If rotor does not turn on distributor shaft, go to next step. 7. Check distributor for proper installation. Repair as necessary. After repairs, go to step 9. If distributor installation is okay, see DIAGNOSTIC AIDS. 8. Replace distributor. After replacing distributor, go to next step. 9. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within the conditionsfor setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2. 10. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTCs are displayed, go to applicable DTC test. DIAGNOSTIC AIDS Check for loose CMP sensor, excessive free play in timing chain and gear assembly, incorrectly installed distributor, loose rotor or distributor hold-down bolt. An intermittent may be caused by a poor connection, rubbed-through wire insulation or a broken wire inside insulation.
The other thing these are known for is the PCM ground, it's on the right cylinder head, on the front or back end depending on the year, they tend to rust, and need to be re grounded.

Merlin2021
Feb 26, 2009.


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