P26E4: Starter pinion-relay open circuit is checked with power commanded on

P26E4 identifies an open-circuit result for the tandem starter’s pinion-relay high-side driver in the cited GM system. The controller makes this assessment with the output powered on. A failure to crank is a broader observation and does not, by itself, identify this monitored electrical condition.

Confirm the command and supply context

The diagnostic compares an internal voltage measurement with controller-specific limits representing an open load. The published impedance criterion is at least 200 kΩ between the signal and controller ground. That is the monitor’s classification basis, not a universal instruction to measure an unspecified connector.

Run/crank voltage must be at least 11 V and the pinion diagnostic enabled. The row accepts engine speed at or above zero; it does not require an already running engine. This matters when interpreting a fault associated with a start request.

Distinguish open, low and high outcomes

The open result requires 40 failed observations out of 50 samples, with 50 ms per sample. P26E5 describes a short-to-ground classification under an on command, while P26E6 assesses short-to-power behavior with the output off. Command state separates these otherwise similar relay labels.

A useful record retains the relay command, supply eligibility and exact fault subtype. The source does not establish whether the interruption lies in the relay, its wiring or the driver, nor does it justify replacing the complete starter.

Source and applicability

2025 GM 25OBDG03B documented monitor only. Vehicle, engine and calibration applicability must be confirmed from the matching service information; no model fitment is inferred. These criteria explain controller logic, not a complete repair procedure. 25OBDG03B, PDF page 853. 25OBDG03B, PDF page 854. 25OBDG03B, PDF page 855.