P01D2 Cylinder 4 Injection Timing Performance - Over Advanced

Diesel engines must detect when fuel can no longer be injected at the correct crank angle – CARB requires this for every injector individually, hence one code per cylinder. The start of injection is not measured directly: during overrun with fuel cut-off the control module fires a tiny test injection into one cylinder (GM: about 1.5 mm³) and evaluates the resulting speed change at the crankshaft sensor. From this it learns how much extra energizing time the injector needs (Bosch calls this zero fuel calibration). This code means injector 4 needs clearly less energizing time than intended, i.e. it opens too early or delivers too much – GM sets it below −90 µs, after two trips. Documented users are GM's 6.6 litre Duramax (LML, L5P) and FCA's 3.0 litre EcoDiesel; Ford reports the same function under P2B11ff. Bulletins often point away from the injector: GM fixed false settings on 2020–2021 L5P trucks with new software and warns that vibration, for example from off-road tyres, disturbs the evaluation; FCA lists wrong injector correction codes, boost leaks and loose injector clamps.

Likely causes

Symptoms

• Check engine light on (after two drive cycles)
• Louder combustion noise or knocking
• Rough idle
• Possibly smoke

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.