Code 45 - Rich Exhaust Indication

Code 45 indicates that the ECM has seen O2 sensor voltage (at ECM terminal "D7") lower than .7 volts for 30 seconds or more, 1 minute after engine start. The ECM supplies a voltage of about .45 volt between terms. "D6" and "D7". The O2 sensor varies the voltage from 1 volt (rich indication) to .10 volt (lean indication). An open sensor circuit or a bad sensor causes open loop operation.

Fig 1: Flow Chart Code 45: Rich Exhaust Indication

Fig 2: Flow Chart Code 45: Rich Exhaust Indication

Fig 3: Schematic, Code 45: Rich Exhaust Indication

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).

This test allows the ECM to confirm either open or closed loop operation.
A steady light or open loop indicates presence of fault. Grounding circuit 412 causes a low O2 signal voltage. If the ECM and wiring are good, the ECM should recognize the low voltage and confirm the lean signal by turning off the light for at least 15 seconds.
Code 45 WILL NOT be set by a faulty O2 sensor. Code 45 indicates a rich exhaust and diagnosis should begin with these items: Fuel pressure, Leaking injector, HEI shielding, Canister Purge, Coolant sensor, MAP sensor, and TPS.