What are the possible causes of the P12B8 GMC code?
- Contaminated or inappropriate fuel quality
- Worn basic engine components or cylinder compression differences
- Faulty fuel injector
- Fuel injector harness is open or short-circuited
- Poor electrical connection of the fuel injector circuit
| How to fix the GMC P12B8 code?
Start by checking the “Possible Causes” listed above. Visually inspect the wiring harness and associated connectors. Check for damaged components and look for broken, bent, pushed, or corroded connector pins.
| What are the possible symptoms of the P12B8 GMC code?
- Engine light on (or Service Engine Soon warning light)
| What does the GMC P12B8 code mean?
The Engine Control Module (ECM) has the ability to learn injector timing performance. With the engine at operating temperature and in closed-throttle deceleration mode, the ECM will pulse each injector individually and measure changes in crankshaft rotation speed using the input from the Crankshaft Position Sensor (CPS). The ECM will perform this diagnostic under three different fuel rail pressures for each injector. The ECM will adjust the timing of the fuel delivered by each injector to achieve the desired RPM increase. The ECM stores the required injector timing value to increase the crankshaft speed to the desired RPM. If the ECM cannot control an RPM increase for a given injector, the appropriate code will be set for that injector.