Powertrain, generic (extended)

P262B Control Module Power Off Timer Performance

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P262B concerns the timer that keeps counting inside a control module while the vehicle is shut down, used to measure how long it has been off. GM runs two checks on it: a count-up test while run/crank is inactive, failing when two consecutive readings differ by over 1.5 s in 4 of 20 one-second samples, and a range test comparing the hardware timer with a mirror timer at shutdown or restart (deviation above 25 % in the 2014 tables). It is Type B, so the MIL follows on the second trip. GM saw false sets on 2019–2020 CT6 4.2 L engines when the engine cooled faster than expected, for example in wind or an air-conditioned garage (PIP5754: clear the code and keep the ECM), and links P262B to ECM supply or ground faults (PIP5609) and to a lost ignition relay feed (PIT5391).

Likely causes

Poor ECM power or ground connection, momentary supply loss

Ignition relay or its control circuit not supplying the module

Diagnostic calibration too sensitive to fast engine cool-down

Internal timer hardware fault in the control module

Symptoms

MIL on after two drive cycles
Possibly other control module codes stored at the same time

Repair estimate

DifficultyShop_onlyWorkshop job

Parts and labour€40–900

Time0.3–2.5 h

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

Parts involved

control modulemain relay

Related codes

P2610 P0606 P0601 P062B P0513

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