P1345 on Buick: How to Diagnose & Fix
Crankshaft Position - Camshaft Position Correlation
1 Buick model · 1 documented issue · 1 critical · $600-$1,500 repair
P1345 on Buick by model: symptoms, diagnosis and fix
The 1994-1996 LT1 uses a camshaft-driven 'Optispark' optical distributor mounted at the front of the engine, low on the timing cover directly behind the water pump. Its optical disc and low-voltage electronics are extremely sensitive to moisture and oil. Any coolant weep from the water pump above it, a failed crankcase vent hose, engine-bay washing, or driving through water can foul the optical sensor and cause misfires. Because it sits behind the water pump, replacement is labor-intensive. This is the single most notorious LT1 (and therefore Roadmaster) driveability failure. The early design vented poorly; B-bodies, including the Roadmaster, got the vacuum-vented unit for 1994, a year before the Corvette and F-body.
Common Symptoms
- Engine stumble, hesitation, or surge under acceleration
- Audible misfire and rough idle
- Excessive vibration
- Hard starting or no-start when wet
- Check engine light / misfire codes
How to Fix
Replace the Optispark with an AC Delco (vented) unit, and because the water pump has to come off to access it, replace the water pump at the same time. Ensure the distributor vent hoses are correctly routed and clear so condensation can escape. Rule out spark plug wires and plugs first, as those often mimic Optispark failure.
Sources for this issue (2)
P1345 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P1345 mean on a Buick?
P1345 stands for "Crankshaft Position - Camshaft Position Correlation." A manufacturer-specific powertrain code; on General Motors vehicles (Chevrolet, GMC, Buick, Cadillac, Pontiac, Saturn, Isuzu) it is set when the signals from the crankshaft position sensor and camshaft position sensor fall out of their expected relationship - commonly cited as roughly 1.5 to 2 percent of crankshaft rotation out of sync. The PCM needs this correlation to time spark and fuel correctly. Symptoms include a check engine light, rough idle or misfire, hard starting, and stalling. On older GM V6/V8 engines this frequently points to a worn timing chain, a real mechanical repair that should not be ignored. Other makes (including Honda, Suzuki and some imports) assign P1345 a different meaning, so confirm the definition for your make before diagnosing. On Buick it is documented across 1 model: Roadmaster.
What are the most common causes of P1345?
The most common causes of P1345 are: Stretched or worn timing chain / failed chain tensioner or guides (very common on higher-mileage GM engines), Faulty camshaft position sensor, Faulty crankshaft position sensor or damaged reluctor wheel, Loose or improperly seated sensor at its mounting, or wrong sensor installed, Damaged wiring, connector corrosion, or shielding fault on either sensor circuit, Incorrect ignition/cam timing after recent timing component service, Crankshaft position variation relearn not performed after PCM or sensor replacement. The specific cause varies by vehicle.
How much does it cost to fix P1345 on a Buick?
Published repair estimates on Buick range from $600 to $1,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.