Diagnostic Aids

Using the "Scan" tester, observe the block learn values at different RPM and airflow conditions. If the conditions for Code 45 exists, the block learn values will be around 115.

• Fuel system will go rich if pressure is too high. The ECM can compensate for some increase, however, if it gets too high, a Code 45 may be set.
• Check for fuel contaminated oil.
• An open ground circuit No. 453 (ignition module ground to ECM) may result in induced electrical "noise". The ECM looks at this "noise" as reference pulses (RPM). The additional pulses result in a higher than actual engine speed signal. The ECM then delivers too much fuel, causing system to go rich. If this problem occurs, "Scan" tester will show a greater than actual engine speed, which can help in diagnosing this problem.
• Check vapor canister for fuel saturation. If canister is full of fuel, check canister liquid/vapor control and hoses.
• An output that causes the ECM to sense a higher than normal airflow can cause the system to go rich. Disconnecting the MAF sensor will allow the ECM to set a fixed value for the sensor. Substitute a different MAF sensor, if the rich condition is gone when the sensor is disconnected, or test MAF sensor using MAF Tester (J 36101).
• Check for leaking fuel pressure regulator diaphragm by checking vacuum line to regulator for fuel.
• An intermittent TPS output will cause the system to go rich due to a false indication of the engine accelerating.