E045

Code E045:

PFI Oxygen Sensor Circuit:

DESCRIPTION:

The PCM/ECM provides a .45 volt reference signal to the oxygen sensor on CKT 412. When the oxygen sensor is cold (below 200°C), the output voltage will be around 0.45 volts, and the PCM/ECM will keep the system in open loop operation. When warm, a properly operating oxygen sensor will drive the .45 volt reference lower (below .45 volts) to indicate a lean mixture and higher (above .45 volts) to indicate a rich mixture. The oxygen sensor signal voltage will swing from rich to lean rapidly, at least one swing every two seconds, if the PCM/ECM is in good control of the air fuel mixture. When the PCM/ECM sees that the oxygen sensor is not at the cold voltage of 0.45 volts, it will send the system into closed loop operation. In closed loop operation, the PCM/ECM will meter fuel into the engine based on the oxygen sensor readings. Code E045 is designed so that if the oxygen sensor stays at a rich voltage for more than 45 seconds during the test conditions, code E045 will set.

Code E045 can be caused by:

1. Oxygen sensor circuit faults.
2. Air fuel ratio actually rich due to a fuel control or emissions system fault.

TEST CONDITIONS:

1. Codes EO14, EO15, EO16, E021, E022, E026, E027, E031, E032, and E034 all must be clear.
2. Throttle switch open.
3. TPS between 6 and 30 degrees and steady.
4. Coolant temp 58°C or greater.
5. Oxygen sensor ready (closed loop).
6. Not accelerating or decelerating.
7. Engine speed greater than or equal to 800 RPM.
8. TPS 10° or greater and canister purge has purged at full duty cycle for 10 minutes since the engine was running with coolant 80°C or greater.

FAILURE CONDITIONS:

Oxygen sensor stays rich for more than 50 seconds.

ACTION TAKEN:

1. PCM/ECM turns on "SERVICE ENGINE SOON" telltale.
2. PCM/ECM turns on canister purge.

NOTES ON FAULT TREE:

1. With the oxygen sensor disconnected, parameter ED33 should remain at reference voltage (.38 to .63 volts)

2. Checking for PCM/ECM's ability to recognize lean input on oxygen sensor signal CKT 412.

3. The PCM/ECM compares oxygen sensor signal voltage received on circuit 412 to the ground voltage on circuit 413. If the PCM/ECM doesn't have a good ground to the engine on circuit 413, the oxygen sensor can appear falsely high or low. With engine running, use a voltmeter to measure voltage from the oxygen sensor at the exhaust manifold to the PCM/ECM terminal A1. If the voltage is -.05 volts to +.05 volts then the ground is OK. If the voltage is less than -.05 volts or greater than +.05 volts, repair poor ground on CKT 413 between PCM/ECM terminal A1 and the ground at front of engine, right (rearmost) head.

NOTE ON INTERMITTENTS:

Engine running, manipulate the oxygen sensor and PCM/ECM wiring and connectors while observing PCM/ECM parameter ED33. If the fault is induced, ED33 will jump above .63 volts, "ECON" status light will come on. Manipulate CKT 413 ground to the engine and look for a loose ground eyelet or ground eyelet installed in an improper location.

Perform PFI SYSTEM CHECK under "A" CHARTS. See DIAGNOSIS BY SYPMTOMS - "Poor Fuel Economy" and "Excessive Exhaust Emissions, Odors". If the oxygen sensor circuit appears to be OK, go to OXYGEN SENSOR CIRCUIT CHECK under "C" CHARTS, to check for a faulty or contaminated sensor.