Duramax Diesel Injector Timing DTCs Set

Several injector timing-related DTCs may be set along with an illuminated Check Engine light on some 2017-2018 Silverado and Sierra models equipped with the 6.6L Duramax diesel engine (RPO L5P).

The DTCs may include the following codes related to injector timing being retarded or advanced: P01CB, P01CC, P01CD, P01CE, P01CF, P01D0, P01D1, P01D2, P01D3, P01D4, P01D5, P01D6, P01D7, P01D8, P01D9, P01DA; and the following codes related to injectors exceeding the maximum or minimum learning unit: P02CC, P02CD, P02CE, P02CF, P02D0, P02D1, P02D2, P02D3, P02D4, P02D5, P02D6, P02D7, P02D8, P02D9, P02DA, and P02DB.

The Engine Control Module (ECM) has the ability to learn injector timing performance. (Fig. 18) When the engine is at operating temperature, throttle closed and in deceleration fuel cut-off mode, the ECM will pulse each injector individually and measure the changes in rotational speed of the crankshaft using the input from the crankshaft position sensor. The ECM stores the injector timing value.

Fig. 18

Do not replace any fuel injectors if any of the injector timing-related DTCs are set. First address any vehicle or engine vibrations or any other vehicle conditions.

Vehicle vibrations, such as those created by “knobby” or aggressive tread tires may induce or aggravate the injector timing-related DTCs.

After addressing any vibration conditions, clear the DTCs and return the vehicle. GM Engineering is investigating this condition and additional information will be released when available.

– Thanks to John Stempnik

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