P034B code meaning
Crankshaft Position Sensor - Crankshaft Direction Incorrect
Powertrain system Generic code P03xx codes Check engine light
What P034B means
Direction-sensing (bidirectional) crank sensors count the rest position for start-stop even when the crankshaft rocks back after shut-off. In normal running the sensor must never report reverse rotation – if it does, the signal is disturbed. GM sets P034B after at least 3 direction reversals within 10 s at 400 to 2,000 rpm and an airflow of at least 1.5 g/s, after two trips; the diesel uses the same thresholds. GM bulletin 17-NA-317 describes the 3.6 V6 (LFY) in the 2018 Buick Enclave and Chevrolet Traverse: interference in the sensor circuit caused P034B with P0506, low idle or stalling after an autostart, transmission slip above 65 km/h and cruise control dropping out; the remedy was a revised sensor wiring. Result: start-stop disabled, possibly reduced power.
P034B at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P034B
- Check engine light on
- Low idle or stalling after an autostart
- Start-stop off, possibly reduced power
- Follow-on effects such as transmission slip or cruise control dropping out (GM LFY)
Common causes of P034B
- Most likelyInterference in the sensor circuit (wiring routed next to switching lines)
- PossibleDirection-sensing crankshaft position sensor faulty
- PossibleGround or connector fault
- Less likelyTone wheel or air gap
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Crankshaft position sensorSensor wiringEngine control module
What each part of P034B means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 3 | Area: ignition system or misfire. |
| 4B | The exact fault in that area. |
What to do next
- Note P034B and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P034B
What does P034B mean?
P034B means "Crankshaft Position Sensor - Crankshaft Direction Incorrect". Direction-sensing (bidirectional) crank sensors count the rest position for start-stop even when the crankshaft rocks back after shut-off. It is a generic code, so it means the same on every make.
Is it safe to drive with P034B?
Drive gently and only to a workshop. With P034B the car can go into limp mode (reduced power) to protect itself.
Will P034B fail an emissions test?
Yes, it can. P034B is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P034B to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P034B clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.