Diagnostic Aids

Code 45 is most likely caused by one of the following:

• Fuel system will go rich if pressure is too high. The ECM can compensate for some increase. If pressure is excessive, a Code 45 maybe set.
• If an open occurs in circuit No. 453, 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 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.
• A MAP sensor output causing ECM to sense lower than normal vacuum can cause system to go rich. Disconnecting MAP sensor allows ECM to set a fixed value for the sensor. Substitute a different MAP sensor if rich condition is gone when sensor is disconnected.
• An intermittent TPS output causes system to go rich due to a false engine acceleration indication.
• A contaminated O2 sensor can cause a false signal. The ECM will reduce fuel delivery causing a driveability problem. Inspect O2 sensor for silicone contamination from fuel or improper use of RTV sealant.
• A sticking EGR valve creates a rich condition, accompanied by rough idle. Check EGR valve operation.

For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.