after running for a while my check engine light keeps coming on and giving me code 23.

gm lists.
23-m/c solenoid fault (carb)
23-mat sensor low temp (efi/tpi/sfi)
23-est bypass circuit fault (caddilac)

i have tbi. how do any of these relate to me ?
what should i look at ?

thanks
mike

 

does your car have a MAT sensor?...cuz i think thats what it is for fuel injected models. mayb track it down and see if its unplugged or not.

eidt: TBI is fuel injected unless otherwise stated.

 

gramps, thanks. i have a spare one, ill give it a swap.

 

changed mat sensor still code 23. so i ran it with mat disconnected and it threw a diffrent code. any other ideas?

 

well one system can affect multiple systems, if your mat sensor isnt working, your computer is thinking your constantly in cold start so its dumping fuel into it, so you might get a "rich mixture" code, or your O2 sensor isnt working. my only suggestion at this point is take it to a place with a diagnostic machine. i take my car to the dealership when i find problems like that. if after replacing the part it still shows the same code, it could be faulty wiring, bad module, or other parts could be bad and thats the best idea the computer can think of. remember those codes are just a baseline, they can mean nothing most of the time.

 

Code 23 is MAT low...a broken wire can cause this as it's an "open circuit". Code 25 is MAT high ... a short/closed circuit causes this.

Make sure you "clear" the codes. Disconnnecting the battery for a minute will do that.

Stick a 1.4K ohm resistor into the connector for the MAT sensor. It will read as 57*F to the ECM. If you still got a problem, then you most likely have a wiring problem with an "open" circuit. Then you need to look at tracing the 452BLK/GND wire & the 472TAN (MAT Signal) wire.

You can start by jumping the "connector" close to the ECM and tracing backwards. If yo still get it when "jumped" at the ECM, you may have a faulty ECM connection internally.

HTH

 

thanks i will work on that tommorow.

 

O.K. It's tomorrow. On a TBI car, the sensor would be called "IAT" but serves the same function. How did you get a TBI on an '87?