P21E1: Interpreting excessive active-stage current for cylinder 3 injector B

P21E1 is the generic high-circuit code for cylinder 3 injector B. The cited GM injector-3 row describes a short-to-supply category, evaluated by the driver's current during activation. It does not directly measure injector flow or fuel pressure.

The diagnostic has a defined event state

Output current must exceed 3.8 A while the power stage is active. The row specifies three events and requires engine speed of at least 80 rpm, battery voltage within the documented 10.9–25.5 V window and the relevant inhibition conditions to be satisfied.

Those criteria distinguish a matured electrical event from a current value captured in another state. A later inactive output with no current cannot independently prove that the previous active-stage problem has been resolved.

Use the classification to select the right investigation

For this channel, open-load and low-circuit diagnoses rely on inactive-stage voltage observations. Treating all three as interchangeable injector faults would discard the specific evidence P21E1 supplies.

The next useful information is the actual injector B circuit map, command history and driver status. Matching the source channel number to the generic cylinder number does not establish where the connector is located or which injector arrangement a particular engine uses. The code cannot isolate the harness, injector load or internal power stage without additional circuit testing. Its current threshold is not a recommendation to energize the injector manually or a sufficient basis to order a replacement.

Source and scope

2025 GM 25OBDG07A Part 2 monitor tables only; model, engine and transmission applicability are not established by the unresolved application-matrix filename join. These are documented monitor criteria, not a universal repair procedure. GM PDF, physical page 556.