Diagnostic Aids
The following conditions are probable causes of Code 45:
- Fuel pressure is too high. ECM can compensate for some increase in fuel pressure; however, if fuel pressure gets too high, Code 45 will set.
- An open ground in circuit No. 453 (Black/Red wire) may result in electrical noise interference, causing a faulty high engine RPM signal to ECM. The ECM will supply too much fuel, causing system to run rich. Engine tachometer will also indicate higher values than actual values.
- 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 run rich, setting Code 45. Disconnecting MAP sensor will allow ECM to set a fixed value for the MAP sensor. If rich condition goes away when 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, refer to INTERMITTENTS in the TESTS W/O CODES article in this section.