P034A: Crankshaft Position Sensor - Crankshaft Start Position Incorrect

What it means

At engine start the crankshaft position reported by the sensor does not match the calibrated start window — typically a wrong tone-wheel installation, sensor air gap, or PCM not synchronised after a relearn.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The crankshaft position sensor reports crank position to the engine control module, which checks that position during engine start against a calibrated start window. P034A sets when the reported start position falls outside that window, which can follow a sensor or wiring fault, a mispositioned tone wheel, or an incomplete relearn.

Common causes

Most likely first.

1. Crankshaft position sensor or wiring fault
2. Tone wheel installed out of position
3. Crankshaft position relearn incomplete

Symptoms

• Check-engine light
• Hard starting or no start
• Rough running

How to diagnose it

1. Review freeze-frame data and starting behaviour to establish whether the incorrect crank position occurs during cranking or after the engine starts.
2. Inspect the crankshaft position sensor connector and harness for damage, looseness, or contamination.
3. Check live crankshaft position data during cranking for a missing, unstable, or implausible start position.
4. If the sensor signal and wiring are sound, inspect the tone wheel installation and condition using the manufacturer’s procedure.
5. Verify whether a crankshaft position relearn is required and complete it using the manufacturer’s procedure.

Common fixes

• Repair a loose connector or damaged crankshaft position sensor wiring.
• Replace the crankshaft position sensor if it fails the manufacturer’s checks.
• Correct tone wheel position or damage according to the manufacturer’s procedure.
• Complete the required crankshaft position relearn.

Can I keep driving?

Hard starting or a no-start can leave you stranded, so avoid trips where a restart may be needed until the fault is addressed. If the engine starts and runs roughly, limit driving and stop if it loses power or stalls.