P0338: Crankshaft position sensor A circuit signal is too high
Crankshaft position sensor A circuit high input
Severity: Inspect soon
The crankshaft sensor tells the computer engine speed and timing, so a bad signal can cause hard starting, stalling or limp mode. Get it inspected soon.
It gets more serious if:
- Stop: The engine stalls while driving, cuts out, or will not start. Losing the crank signal can stop the engine without warning in traffic.
P0338 in short
P0338 means the engine computer sees too high a signal from the crankshaft position sensor. Causes include a defective sensor, wiring shorted to power, a wrong air gap or water in a connector. It can cause stalling or hard starting, so get it inspected soon and stop driving if the engine cuts out.
The computer uses the crankshaft sensor to know engine speed and when to fire spark and fuel. P0338 sets when the voltage from the sensor is too high.
Some engines run without noticeable symptoms because the computer can estimate crank position from the camshaft sensor, which is why the check engine light may be the first sign.
Most likely causes
These are general causes for this code across vehicles. None is specific to one make or model.
Cause 1: Failed crankshaft position sensor
Common general cause- Why it ranks here
- TroubleCodes.net lists an internal sensor failure among the main causes of this code.
- What would change this
- Rises if the signal is missing or abnormal on a scope while cranking. Falls if the signal is clean.
Cause 2: Sensor misaligned or wrong air gap
Common general cause- Why it ranks here
- TroubleCodes.net lists poor alignment or an incorrect air gap as a cause; the sensor reads the tone wheel through a small gap.
- What would change this
- Rises after recent work near the sensor or if it is loose. Falls if it is mounted correctly.
Cause 3: Wiring or connector fault
Common general cause- Why it ranks here
- A wire shorted to positive voltage, water or corrosion in a connector can push the signal high.
- What would change this
- Rises if the harness shows damage, water or corrosion, or wiggling it changes the signal. Falls if wiring tests good.
Cause 4: Engine computer fault
Possible — needs testing- Why it ranks here
- TroubleCodes.net lists a computer fault only after the sensor and wiring pass.
- What would change this
- Rises only if sensor and circuit tests all pass. Falls otherwise.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: With the engine off and cool, check the crank sensor connector, harness and mounting for damage, water or looseness.
Warning:Engine off and cool; the sensor is often low on the engine near the exhaust or starter, so support the car on stands if you must go underneath.
IfWiring damaged, wet or corroded
It meansRepair the wiring.
IfSensor loose or misaligned
It meansRemount it with the correct air gap.
IfAll looks fine
It meansCheck the signal.
Step 2: Have a shop check the crank signal with a scope or multimeter while cranking, and verify the reference voltage and battery cranking speed first.
Warning:Cranking the engine with tools clipped to sensor wiring puts hands near belts and the starter; leave it to a shop.
IfSignal missing or abnormal with good wiring
It meansReplace the sensor.
IfSignal is fine on a scope
It meansComputer fault is possible.
Symptoms
- Check engine light on
- Long cranking or no start Gets more serious: stop and have it checked.
- Stalling or misfire Gets more serious: stop and have it checked.
- Lack of power or limp mode
How to fix
On your vehicle
CadillacYour car
1999–2000 · Escalade
Supported by vehicle dataNHTSA flat-file summary of Cadillac bulletin 000604014-cadillac (summary: customers may report hard, no or slow starting, backfire or kickback during crank, grinding or unusual noises during crank, and P0338). Whether it is still current is not verified.
000604014-cadillacStatus unverified
Hard start, backfire and P0338
1999–2000escalade · issued · NHTSA 6091427
NHTSA flat-file summary only; the full bulletin was not read. The summary mentions customers may report hard, no or slow starting, backfire or kickback during crank, grinding or unusual noises during crank, and P0338.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
Related codes
Sources and review
- Diagnostic Trouble Code (DTC) list
- P0338 code summary
- 000604014: Hard start, backfire and P0338
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error