Code 45....running out of things to check!


New Member
May 25, 2001
Recently my car has been running really can smell raw fuel and the car lunges under any acceleration. Here is the info i got from on that code:

Trouble Code 45 indicates that the O2 sensor is showing a persistently low exhaust oxygen content (rich), despite the efforts of the ECM to decrease injector on-time (thus decreasing fuel delivered). Integrator and BLM numbers may indicate < 128 by a substantial margin.

The conditions for setting this code are:

no Code 34 or Code 35 (MAF error) present, and
the O2 sensor voltage remains above 752 mV, and
the ECM is in Closed Loop control, and
throttle position is < 2 percent or > 20 percent, and
the above conditions exist for more than 20 seconds.

Typical causes for this code include:

1) O2 sensor defective or contaminated (if incorrect RTV sealant or too much RTV is used, this may happen)
2) Leaking fuel injectors
3) Fuel pressure too high
4) EMI interference from poor plug wires
5) Evaporative Emission system defect
6) TPS and/or EGR problem
7) MAF sensor reading higher airflow than is actually present
Here is what i have looked at so far corresponding to the list above:

1. from my scanmaster o2 readings i assume the o2 sensor is is bouncing back and forth in the number range it should be.

2. don't know how to check for leaky fuel injectors...but i just the blue tops about 3000 miles ago.

3. fuel pressure is set correctly

4. tried different set of plug wires and replaced plugs

5. Don't know how to check this

6. throttle position sensor has correct values at full an no throttle and egr seems to function correctly(if you push up on the bottom of the diaphram the car stumbles)

7. Don't know to check this

Any help or suggestions would be greatly appreciated.

I've seen a header leak cause what you see. Be sure everything upstream of the sensor is tight and there are no leaks.

If you are wondering about a leaking injector, usually you will exhibit a hard, rich start up and you lose fuel pressure on the rail fairly soon after a shutdown. You could pull the plugs after the car cools and see which plug is dripping with fuel.

It does not lose fuel pressure quickly after shutting down the engine so i assume the injectors are not leaking.

The blms stayed around 115 for the most part...bounced around some between 100 and 125.

Also the car seems to run ok for the first minute or so, but after it starts to warm up a little it starts to lunge bad under any acceleration.

Is their any way to test the MAF sensor before i spring $120+ on replacement?
Can't reeeeally test the MAFs, best way is borrow one from someone for a few minutes,, don't laugh, i've lent mine out a couple times. I wouldn't suggest buying one until you varify that's the prob.
Sounds like it's ok in open loop. Have you tried a new AC Delco O2 sensor? The BLMs don't sound thaaat bad. At least they're not pegged at 90 or 150.
Also, have you checked the Cam sensor setting?
Before replacing any parts, I suggest trying lower fuel pressure. :)