Code 45, Lean Exhaust Indication
The ECM supplies a voltage of about .45 volt between terminals No. 3 and 20. (If measured with a 10-megaohm digital voltmeter, this may read as low as .32 volts). The O2 sensor varies voltage within a range of about one volt if exhaust is rich, down to about .1 volt if exhaust is lean. The sensor circuit acts like an open circuit until the sensor is above 600°F (315°C). An open sensor circuit or a defective sensor will cause open loop operation. Code 45 indicates the ECM has sensed O2 sensor voltage under the following conditions: voltage higher than specified, closed loop, above 25% TPS value, for about one minute and above 2000 RPM.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- A dwell under 50 degrees indicates engine should be checked for cause of intermittent rich condition. Check for purge or bowl vent valves leaking, fuel in crankcase or evaporative canister, or sticking M/C solenoid.
- This step puts a lean condition, into engine to see if ECM can respond. A drop in dwell indicates ECM and O2 sensor are not faulty.
- This step checks ECM response to a lean O2 sensor signal.
- This step checks voltage from ECM at O2 sensor harness. Normal voltage at this point is ECM bias voltage for no O2 signal, which is approximately .45 volt. If voltage is high, wire to ECM could be shorted to battery positive or fault is ECM.
- This step determines if there is an open or short in wire from O2 sensor connector to ECM terminal No. 3, or if ECM is faulty.