DTC 45

Fig. 036 - Wiring Diagram for Code 45 Rich Exhaust Indication. VIN C:

CODE 45, RICH EXHAUST INDICATION

The ECM supplies a voltage of about .45 volt between terminals "3" and "20". (If measured with a 10 megohm digital voltmeter, this may read as .32 volts.) The O2 sensor varies the voltage within a range of about 1 volt if the exhaust is rich, down through about .10 volt if exhaust is lean.
The sensor is like an open circuit and produces no voltage when it is below about 360°C (600°F). An open sensor circuit or cold sensor causes open loop operation.
Trouble Code 45 says that the ECM has seen:
a. High oxygen sensor voltage
b. More than specified time and RPM (about 1 minute above 2000 RPM)
c. Above a 25% TPS value
d. Closed loop
e. A high voltage can be caused by a rich exhaust.

Fig. 035 - Chart - Procedure For Code 45 Rich Exhaust Indication.:

1. Checks to see if fault is still present. A dwell of under 50° indicates engine should be checked for cause of intermittent rich condition: i.e.,
a. Purge or bowl vent valves leaking.
b. Fuel in crankcase.
c. Fuel in evaporative canister.
d. Sticking mixture control solenoid.
2. This step puts a lean condition, air leak, into the engine to see if ECM can respond. A drop in the dwell indicates ECM and O2 sensor are not faulty and look for source of constant rich condition. See step one examples.
3. This step tests to see if ECM is able to respond to a lean exhaust O2 signal (low voltage).
4. This step checks the voltage from the ECM at the O2 sensor harness. Normal voltage at this point is the ECM bias voltage for no O2 signal which is approximately .45V. If voltage is high, the wire to the ECM could be shorted to B+ or it is a faulty ECM.
5. This step determines if there is an open or short in the wire from the oxygen sensor connector to ECM terminal "3" or if it's a faulty ECM.