Powertrain, generic (extended)

P2534 Ignition Switch On/Start Position Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Engine harness chafed at a bracket (GM HD trucks, upper control arm bracket)
Run/crank relay or fuse open
Module software needing an update (GM 6L50 TCM, Ram eTorque HCP)
Loose terminal on the wakeup line at TCM or BCM

Symptoms

  • MIL on
  • Stall or no start
  • Transmission or other modules set follow-up codes

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–500
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

ignition switchwiring harness

Related codes

P2533P2535P2531P0700

References: gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov.