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.

• Check for short to voltage in circuit No. 412.
• Check for leaking injector(s). See CHART A7.
• 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. See CHART A7.
• An open in 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 for fuel contaminated oil.
• Check vapor canister for fuel saturation. If canister is full of fuel, check canister liquid/vapor control and hoses.
• 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.
• An EGR valve staying open (especially at idle) will cause the O2 sensor to indicate a rich exhaust. This could result in a Code 45.