Engine Positions System Performance Bank 1
Code P0008 means the PCM has detected that the camshaft and crankshaft positions on Bank 1 are not synchronized within the expected range — an "engine position system performance" fault. This usually means the variable valve timing system is not achieving its commanded position, or the timing chain has stretched enough to shift the cam timing relationship. P0008 is common on GM vehicles (Cadillac, Chevrolet, GMC) with variable valve timing engines and on any high-mileage engine with a worn timing chain.
What You Might Notice
- Check engine light on
- Rough idle or engine vibration
- Poor fuel economy
- Reduced power, especially on acceleration
- Timing chain rattle at startup (cold)
- Rough running that improves after warm-up
Most Common Causes
- 1
Stretched or worn timing chain
The most common cause of P0008. A stretched timing chain allows the camshaft to drift from its correct position relative to the crankshaft. Chain stretch is gradual with mileage and is especially common in engines that have had infrequent oil changes.
- 2
Worn or faulty timing chain tensioner
A failing hydraulic tensioner cannot maintain proper chain tension, allowing slack that shifts cam timing. A rattling noise at cold startup that disappears after warm-up is a strong indicator of a failing tensioner.
- 3
Crankshaft reluctor wheel has slipped
On some engines, the crankshaft reluctor wheel is pressed onto the crankshaft. If it slips even slightly, the PCM's reference point for crankshaft position shifts, causing a false cam/crank correlation fault even if the chain is fine.
- 4
Failed or stuck variable valve timing solenoid (Bank 1)
If the VVT solenoid is stuck or not receiving adequate oil pressure, the camshaft cannot be commanded to the correct position, setting P0008. Check for low oil pressure and inspect the VVT solenoid screen for debris.
- 5
Low or dirty engine oil
Variable valve timing systems are oil pressure-driven. Low oil level or sludgy oil from infrequent changes prevents the VVT system from operating correctly and can cause timing correlation codes.
How to Diagnose It
- 1
Check Stretched or worn timing chain — The most common cause of P0008. A stretched timing chain allows the camshaft to drift from its correct position relative to the crankshaft. Chain stretch is gradual with mileage and is especially common in engines that have had infrequent oil changes.
- 2
Check Worn or faulty timing chain tensioner — A failing hydraulic tensioner cannot maintain proper chain tension, allowing slack that shifts cam timing. A rattling noise at cold startup that disappears after warm-up is a strong indicator of a failing tensioner.
- 3
Check Crankshaft reluctor wheel has slipped — On some engines, the crankshaft reluctor wheel is pressed onto the crankshaft. If it slips even slightly, the PCM's reference point for crankshaft position shifts, causing a false cam/crank correlation fault even if the chain is fine.
- 4
Check Failed or stuck variable valve timing solenoid (Bank 1) — If the VVT solenoid is stuck or not receiving adequate oil pressure, the camshaft cannot be commanded to the correct position, setting P0008. Check for low oil pressure and inspect the VVT solenoid screen for debris.
- 5
Check Low or dirty engine oil — Variable valve timing systems are oil pressure-driven. Low oil level or sludgy oil from infrequent changes prevents the VVT system from operating correctly and can cause timing correlation codes.
How to Fix It
- 1
Check and change the engine oil
Verify oil level and condition. If the oil is dark, sludgy, or overdue for a change, perform an oil and filter change first. Many P0008 codes on high-mileage engines clear after an oil change if the VVT system was just oil-starved.
- 2
Inspect and clean the VVT solenoid and screen
Remove the Bank 1 variable valve timing solenoid and inspect the oil screen/filter for sludge or debris. Clean or replace the screen. Test the solenoid for proper resistance and operation.
- 3
Listen for timing chain rattle and check chain stretch
A cold-start rattle that disappears after warm-up is a classic sign of a stretched chain or failing tensioner. Have the timing chain slack measured against specification if internal access is possible.
- 4
Replace the timing chain kit
If the timing chain is confirmed stretched or the tensioner is worn, replace the complete timing chain kit — chain, tensioners, guides, and sprockets. Partial replacement often leads to repeat failures.
- 5
Clear codes and verify cam/crank timing with a scanner
After repairs, clear all DTCs and use a scan tool to monitor cam/crank correlation live data. Confirm Bank 1 timing is within specification across all RPM ranges before returning the vehicle to service.
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