- Self-Diagnostic System Check

Some failures of this system will result in an "Engine Cranks But Won't Run." If this condition exists, refer to Chart A-3 in Computers and Control Systems / System Diagnosis / Diagnostic Charts. This chart will determine if the problem is caused by the ignition system, Electronic Control Module (ECM) or fuel pump circuit.

If it's determined to be a fuel problem, refer to Chart A-7 in Diagnostic Charts. This includes the injectors, pressure regulator, fuel pump and fuel pump relay.

The fuel system wiring schematic diagram is covered in Trouble Code 54, see Diagnostic Charts. If a problem occurs in the fuel metering system, it usually results in either a rich or lean exhaust condition. This condition is sensed by the oxygen sensor and causes the ECM to change the fuel calculation (injector pulse width).

The change made to the fuel calculation will be indicated by a change in the integrator and block learn values, which can be monitored by a "Scan" tool. A short term change to the fuel calculation is indicated by the integrator value, while a long term change is indicated by the block learn value. Average integrator and block learn values will be around 128, but may vary slightly from engine to engine. Refer to Computers and Control Systems / System Diagnosis / Scan Tester Diagnosis for further diagnostic information for block learn values.