Diagnostic Aids

Code 45 is most likely caused by:

• Fuel pressure too high. ECM can compensate for some increase in fuel pressure; however, if fuel pressure gets too high, a Code 45 will set.
• An open ground in circuit No. 450H may result in electrical noise interference causing a faulty high engine RPM signal to ECM. The ECM will supply too much fuel, causing the system to run rich. Engine tachometer will also show higher than actual readings.
• Check for fuel saturation of canister and for faulty canister purge control.
• A false MAP sensor signal indicating lower vacuum than normal manifold vacuum can cause system to go rich exhaust, setting a Code 45. Disconnecting MAP sensor will allow ECM to set a fixed value for the MAP sensor. If rich condition goes away while MAP sensor is disconnected, substitute a known good MAP sensor.
• An intermittent TPS signal giving false indication of engine acceleration will cause rich exhaust and Code 45 to set.
• A contaminated O2 sensor will provide a false high reading to ECM. The ECM will reduce fuel delivery, causing a severe surge driveability problem.
• EGR valve sticking or leaking will cause dilution of exhaust gases and will cause ECM to richen fuel system mixture. If Code 44 is intermittent, see INTERMITTENTS in H TESTS - W/O CODES article.