Diagnostic Aids
Code 45 or rich exhaust is most likely caused by one of the following:
- Check for fuel contaminated oil.
- If an open occurs on circuit No. B2, HEI induced electrical noise may result, causing simulated reference pulses to be picked up by ECM. Additional pulses result in a higher than actual engine speed signal. The ECM will increase injector pulse width to match fuel requirements of increased RPM signal. Tachometer will show higher than actual RPM, which can help in diagnosing this problem.
- Check charcoal canister for fuel saturation. If full of fuel, check canister control and hoses.
- An output causing ECM to sense a lower than normal vacuum can cause system to go rich. Disconnecting MAP sensor allows ECM to set a fixed value for the sensor. If rich condition is gone with MAP sensor disconnected, replace sensor.
- An intermittent TPS output causes system to go rich due to a false acceleration indication.
- Inspect oxygen sensor for silicone contamination from fuel, or use of improper RTV sealant. Sensor may have a White powdery coating and result in a high but false signal voltage (rich exhaust). ECM will reduce amount of fuel delivered to engine, causing a severe surge driveability problem.
- Check for EGR valve sticking open at idle, usually accompanied by a rough idle or stall complaint, especially at idle.
For intermittent inspection, see INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.