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 in distributor ground circuit (Black/White 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 45 is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section.