Some 2022-2023 Trailblazer and Encore GX models equipped with the 1.3L engine (RPO L3T) may have an illuminated Check Engine MIL and DTC P2B95 (Injection Pulse Performance During Cold Start) set in the Engine Control Module (ECM). (Fig. 9)
These conditions may be due to a fuel injector variation with the converter light off. The ECM should be reprogrammed with an updated calibration to address the injector variation.
Fig. 9
During a cold start, the ECM commands dual-pulse mode during Open Loop operation to improve cold start emissions. In dual-pulse mode, the injectors are energized twice during each injection event.
The catalyst must be warmed to efficiently reduce the emissions. The cold start emission reduction control system strategy is to reduce the amount of time it takes to warm the catalyst. During a cold start, the engine spark timing is altered to allow the catalyst to warm quickly.
Fuel trim bias is used to keep the post catalyst air/fuel ratio within a predetermined range. This allows optimal catalyst efficiency under various operating conditions. The ECM constantly monitors how lean or rich the fuel trim bias is commanded, to determine if the fuel trim bias is greater than a calibrated amount.
For more details, refer to Bulletin #23-NA-022.
– Thanks to Matthew Gager
