Engine Misfire Detected without Drivability Concerns

An engine misfire DTC may be set on some 2020-2021 Silverado 1500 and Sierra 1500 models equipped with the 5.3L V8 engine (RPO L84). However, the misfire may not be noticed by the driver or the vehicle may not have any drivability concerns. The Check Engine MIL may be illuminated (Fig. 8) or may have been flashing while driving up a long grade or a smooth road with steady throttle input. DTC P0300 (Engine Misfire Detected) may be set as active or history in the Engine Control Module (ECM).


Fig. 8


The detected misfire condition may be the result of the P0300 diagnostic falsely setting the DTC under certain driving conditions. GDS2 data may show misfires being recorded on any cylinder, but they may be more noticeable on cylinders 1 and 6.

To address the detected misfire condition, an updated calibration has been released. Reprogram the ECM with the latest calibration and perform the Crankshaft Position Variation Learn procedure. Do not replace any parts for the condition.

TIP: To avoid warranty transaction rejections, the warranty claim code provided on the SPS Warranty Claim Code (WCC) screen must be recorded on the job card (repair order).

The updated calibration does not address any true engine misfire. It only updates the P0300 diagnostic in the ECM. If the engine is actually misfiring, refer to the appropriate Service Information for additional diagnostic information.

Once the calibration has been updated, drive the vehicle and verify the DTC does not set.


Crankshaft Position Variation Learn Procedure

The Crankshaft Position Variation Learn procedure must be performed or the updated calibration will not provide the desired results.

The crankshaft position sensor variation or reluctor ring learn is used to calculate reference period errors caused by slight tolerance variations in the crankshaft and the crankshaft position sensor. The calculated error allows the ECM to accurately compensate for reference period variations, which enhances the ability of the ECM to detect misfire events over a wider range of engine speed and load. The compensation values are stored in ECM memory after a learn procedure has been performed.

For additional information, refer to Bulletin #21-NA-154.


– Thanks to Bryan Salisbury

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