So my car throws a code 45 but only after sitting idling for 2 or 3 minutes It also hesitates and almost dies when it's cold and gently step on the throttle, but if I just punch it it revs all the way up no problem. TPS is good no deadspots, CTS ohm's are good, the O2 sensor has been replaced and the MAP sensor is good. I have a MAT sensor on the way, the only thing I haven't checked is the IAC motor is there a way to check this? the car is an 87 Fiero 2.5l 60,000 miles It was sitting for 5 or 6 years until I revived it recently.

Code 45
Oxygen Sensor - Rich Exhaust
The ECM will set code 45 when the ECM detects a high voltage from the oxygen sensor, throttle is applied and the system is operating in Closed Loop (conditions must exist for longer than 50 seconds and engine must be running for at least 1 minute).

Check the oxygen sensor and replace if necessary.

Check fuel pressure. The system will go rich if the fuel pressure is too high.

Check for rich injectors.

Check for leaking injectors.

Check for fuel contamination (specifically for contamination with oil).

Check for proper ignition module shielding. If the ignition module is not properly shielded, the ECM might mistake the electro-magnetic interference for reference pulses, causing too much fuel to be delivered to the system.

Check the canister purge for fuel. If full, check canister control and hoses.

Check the MAP sensor. If the ECM detects a lower than normal vacuum then this will cause the system to go rich. Disconnect the MAP sensor. If the rich condition goes away, then a problem exists with the MAP sensor.

Check for leaking fuel pressure regulator by checking the vacuum line to the regulator for fuel.

Check TPS. An irregular TPS output will cause the system to go rich due to a false indication of accelerating.

Code 45 w/ idling engine... Been there, done that....
Replace MAT sensor.
See my cave... DIS and 700 TBI (Show MAT location) in 4 cyl engine section.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

Well I put the new one in and it didn't change anything. What is the resistance supposed to be? Your cave says 150 is high and 3500 is low but what is it supposed to be at say 70 degrees?

Well it was probably 80 when I tested them but my old one was 2000 and the new one was 2200

When you checked the MAP sensor did you back probe the center (Greeen) pin and read the voltage to ground (or better yet to the black or orange/black wire of the MAP)

Backprobe = have the connector still plugged in but take a long pin and shove it the backside past the rubber seal till you can read the voltage of the working circuit.

Generic Backprobe pix


Did you read them engine off key on, and engine at idle?

Key on - engine off


Key on - engine idling


Figure about the 1.5 - 1.7v range idling. It should pop up a fair amount when you pop the throttle open. When you snap it back it should drop to below idle for a bit and then come back up to the idle reading.

You should read +5v on the Gray wire - Black or engine as ground.

[This message has been edited by phonedawgz (edited 09-09-2011).]

KOEO Running
RED/BLACK 26mv 19mv
Green 4.6v 23mv
Grey 8mv 9.4mv

This is what I got

I'm pretty sure when it was reading millivolts, that he probe/pin wasn't making contact. Try again but push the pin farther in till you get a reading in the volt range - except it's ok for millivolts on the black wire.

Okay lets try this again:
KOEO Running
red and black 20mv n/a
Green 4.6 1
Grey 5v 20mv

On the N/A it was all over the place not consistent whatsoever, and on the mv readings I tried several times and consistently got the same numbers.

Try this...
Turn on fuel pump (12+ to ALDL pin G. See cave, aldl in ECM section)
Check injector and make sure it's not leaking fuel. Injector uses 2 O-ring...

Test fuel pressure. see TBI adapter in 4 cyl engine in cave

Maybe buy/borrow ecm scan tool. Sorry No, WinALDL won't read your ECM... See scan tool help in cave.

Small leaks or high pressure can cause DTC 45 at idle. This ECM likes to run engine at 128 BLM at idle. 128 is max for not setting DTC 45.

[This message has been edited by theogre (edited 09-12-2011).]

Well I bought a cable do you know of a scanning software that will work with a 7730 ecm? or the efi live definition file name?

quote Originally posted by Garrettpen98: ... a 7730 ecm ...

You waited until now to mention this? Are you sure your ECM is a 7730?

[This message has been edited by Marvin McInnis (edited 09-16-2011).]

quote Originally posted by Garrettpen98: the car is an 87 Fiero 2.5l 60,000 miles It was sitting for 5 or 6 years until I revived it recently.

Car uses 1227748 not 7730... (7730 is commonly use w/ V6...)
7748 not = to 7730 and most/all free scan software doesn't support 7748. Need a commercial OBD1 scanner.

[This message has been edited by theogre (edited 09-16-2011).]