P2534Ignition Switch On/Start Position Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2534 is the most widely documented of this group. GM's 2025 tables let the TCM fail it when its run/crank input is false while the ECM reports run/crank active, 99 failures out of 240 samples at 25 ms, Type A; the brake control module (EBCM) sets it when its primary wakeup line reads low for 3 s while the network says run or crank, Type B. On the 2016 Volt the line must drop below 2.0 V for 2.5 s. GM bulletins name an ECM harness rubbed through where it passes the left upper control arm bracket on 2020–2025 Silverado/Sierra 2500HD/3500HD (24-NA-124: MIL, stall, no start) and a TCM recalibration for 2008 CTS/STS with the 6L50 (PIP4276B). Ram's 08-037-21 lists it for the 2021 eTorque 1500. Ford's 2014 BOSS 302S table carries it without the M marker.
- What you may notice
- MIL on
- Stall or no start
- Transmission or other modules set follow-up codes
- Likely causes
- LikelyEngine harness chafed at a bracket (GM HD trucks, upper control arm bracket)
- PossibleRun/crank relay or fuse open
- PossibleModule software needing an update (GM 6L50 TCM, Ram eTorque HCP)
- RareLoose terminal on the wakeup line at TCM or BCM
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €0 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.