P2538: Ignition Switch Accessory Position Circuit High
The ACC input reads stuck high — short to battery voltage. The ECM cannot detect when the operator releases the switch from ACC, accessory power timeouts do not work.
What P2538 means
P2538 is a generic OBD-II powertrain code in the speed, idle & cruise group. In plain English: the computer sees a voltage on that circuit that is higher than it should ever be — often an open ground, a short to power, or a failed sensor.
- Check engine light
- Usually on
- Emissions-related
- No
- Limp mode possible
- Not typical
- Drive cycle to clear
- Not required
Get it fixed
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Common causes
- 01ACC wire shorted to battery voltageMost likely
- 02Connector pins corroded - high contact resistanceLess likely
- 03Supply wire pinched against B+ sourceLess likely
Can I drive with P2538?
Usually yes, for a short time.
The car will often drive normally, but get it diagnosed soon. If you notice rough running, warning lights flashing, overheating or a burning smell, stop driving.
Why we rate it moderate
- Turns on the check engine light
Severity is our rule-based rating from the code’s flags in OBDex and the system it affects, not an inspection of your car. If the check engine light is flashing, or you notice overheating, low oil pressure, or brake or steering problems, stop driving and get help.
How to diagnose P2538
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just P2538. Save the freeze-frame data (speed, load, temperature when the fault set) before clearing anything; it tells you when the fault happens.
- 2
Check for related codes first
Look for P2536, P2537. Related codes often share a cause; a circuit or sensor code usually needs fixing before a performance code like this one.
- 3
Test the circuit
Inspect the wiring and connector at the ignition switch and wiring harness for damage, corrosion or chafing. With a multimeter, check supply voltage, ground and signal against the specifications in the service manual for your vehicle.
- 4
Test the likely causes in order
Start with the most likely cause and work down: ACC wire shorted to battery voltage; connector pins corroded - high contact resistance; supply wire pinched against B+ source. Test before replacing parts.
- 5
Check for recalls and service bulletins
Look up recalls for your exact vehicle with its VIN, and ask a dealer about technical service bulletins (TSBs). Manufacturers sometimes issue software updates or extended warranties for known faults.
- 6
Clear the code and verify the repair
After the repair, clear the code and drive the car under the conditions in the freeze-frame data to confirm it does not return.
P2538 repair cost estimate
Estimate, not a quote. Labor times are typical ranges for this code from OBDex, and $125/hr is an assumed rate. Shop rates and labor times vary by vehicle and region. Diagnosis time may be billed separately.
- DIY difficulty
- Moderate
- Good DIY job?
- Usually a shop job
Needs a scan tool and some experience with testing.
Parts and systems involved
- Ignition switch
- Wiring harness
P2538 FAQ
What does P2538 mean?
P2538 means “Ignition Switch Accessory Position Circuit High”. The ACC input reads stuck high — short to battery voltage. The ECM cannot detect when the operator releases the switch from ACC, accessory power timeouts do not work.
Is P2538 serious? Can I keep driving?
We rate P2538 as moderate severity. Usually yes, for a short time. The car will often drive normally, but get it diagnosed soon. If you notice rough running, warning lights flashing, overheating or a burning smell, stop driving.
What causes P2538?
The most common causes, from most to least likely: ACC wire shorted to battery voltage; Connector pins corroded - high contact resistance; Supply wire pinched against B+ source. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix P2538?
Typical labor is about $65–$250 at an assumed $125/hour shop rate, plus parts. That is an estimate, not a quote: labor times and rates vary by vehicle and region, and diagnosis may be billed separately.
Can I fix P2538 myself?
DIY difficulty is moderate. Most owners leave this to a shop because it needs involved testing or specialist tools. Always confirm the cause before buying parts.
Will P2538 clear itself?
If the fault was intermittent, the warning may go off once the computer stops seeing it, but the code stays in memory. Fix the cause; clearing the code alone doesn’t repair anything.