Hi,
I have a 1986 Pontiac trans am with 305 TPI. All Stock. Lately I have been getting a code 45 ONLY when I drive highway speed 70-90 MPH. Otherwise nevers comes on. Also goes away after turn off engine and doesnt come on during city driving. No issues with driving car (i.e. not stalling, running bad, etc.)

Any idea why I am getting this? I checked VACUUM hoses, etc. and look good. car has 100K and is mint.

Just annoying to see that SES light come on as I do alot of highway driving.

Any input appreciated. thanks.

 

Code 45 is "Oxygen sensor rich exhaust indicated". It means that the O2 sensor is reading rich when the vehicle is a cruise speeds. Generally, if the EFI system was actually stuck rich, you would notice it in vehicle performance and fuel economy. More likely the O2 sensor is just on its way out. The O2 sensor threads into the drivers side exhaust manifold, just before the manifold meets the exhaust pipe. It takes a 7/8" wrench to remove it and replace it. The code will clear itself from memory after 50 engine starts without a failure.

 

Code 45 appears to be the result of the o2 sensor reading a rich(er than normal) mixture. No real easy way to go about this, you'll need to check your mixture under those conditions. Are you noticing a decrease in fuel economy? Anything that might corroborate the rich mixture code, or perhaps using more fuel? Check your spark plugs for fouling?

Will

 

Sorry for delay. No decrease in fuel consumption acutally getting 24 mpg with 87 octane. I do all highway driving. No issues although today it did stall but started right up.

So really no issues except again when cruising at 70-80 mph it comes on. I tried (although quickly) to get that O2 sensor out but had no luck. Am I supposed to get to from underneath car? I have an o2 sensor socket but there is so much stuff in the way I was unable to turn the ratchet. Any advice. I have a feeling that is my problem and bought a new one. just need to replace. thanks

 

I found it easier to change from underneath.