[White98bu]

ok 1998 malibu 3.1 have check engine light when i turn the key on and it goes out after startup put code reader on it (snap on so it is not a cheap one) tells me ses light is on but it isnt on the dash code shows iat sensor voltage high have replaced it with a known good one still get code checked continuity of iat wires they are good to the ecm there are no drivability issues at all car runs like a raped ape my question is could the ecm lost its drivers for this or could it be a bad ecm and will a ecm form the exact same year,model go in w/o any reprogramming issues i work in a pull it yourself yard so the parts arent a prob and what cpu in the car holds the vin cause if need be i will grab that also thanx for all your help in this

 

[Silver LTZ]

You sure it isn't just lighting up at start-up like it is meant to for a second? If the code says IAT and you replaced it, and checked the wires you should be okay if you say it runs so good. Next post, please try using periods. I got a headache trying to read that!

 

[White98bu]

Sorry about no periods. I flunked grammar class in high school. LOL Yes it does at startup,But my scanner says the light is on but it is not on the dash.Besides the iat is showing -39deg this may be just a pita that may never get resolved. Thanx for your reply if you happen to come up with any more ideas please let me know. thanx again

 

[Silver LTZ]

Sorry about no periods. I flunked grammar class in high school. LOL Yes it does at startup,But my scanner says the light is on but it is not on the dash.Besides the iat is showing -39deg this may be just a pita that may never get resolved. Thanx for your reply if you happen to come up with any more ideas please let me know. thanx again

Weird that the scanner says it's on when it is not. You know it works cause it came on and goes off. Have you tried another scanner? Tried pulling the IAT to see if the light stays on? If that is all good the other end of the sensor wire might be bad, or the harness itself.

 

[White98bu]

ok so i just came in from doing a little dianostic work on the ol bu. have found out from the trusty vom that i dont have the 5v ref sig. now can i tap into the 5v from the tps to get the 5v that i need i know it is kind of a jury rig but this will be just to test it . plus i pulled the tps plug with the reader hooked up it said ses light was on yet i had nothing on the dash i know the lights are led. i also noticed i have a ses light and check engine light(which does not work). could the light be burnt out? or is it highly unlikely and why is there 2 different service light on this car ?

 

[Starship]

ok so i just came in from doing a little dianostic work on the ol bu. have found out from the trusty vom that i dont have the 5v ref sig. now can i tap into the 5v from the tps to get the 5v that i need i know it is kind of a jury rig but this will be just to test it . plus i pulled the tps plug with the reader hooked up it said ses light was on yet i had nothing on the dash i know the lights are led. i also noticed i have a ses light and check engine light(which does not work). could the light be burnt out? or is it highly unlikely and why is there 2 different service light on this car ?

What Silver said. If the code is P0113, it means the voltage drop across the IAT is >= 5V. Combined with the absence of the 5V at the IAT sensor, I think you have a break in the wiring, connector, or the harness at the ECM.

On the other issues, you should try another scanner. What happens if you reset the light with the scanner? Does the lamp then turns on?

Oh, splicing in a 5V source at the IAT won't work. The voltage drop is measured inside the ECM.

 

[White98bu]

i have figured out the check engine light does not work but the ses light does. I figured this out by disconnecting the tps and the check engine light does not come on. if i reset the light by the scanner it shows no codes on the scanner and it shows the check engine light to be off. i think the check engine light is burnt out. as for tapping into a 5v source doesnt the ecm read off of the ground wire? So if it reads resistance off the ground it really shouldnt matter where the ref sig comes from as long as it can read the resistance on the ground wire right? and one more thing are the idiot lights replacable or not. it is (check engine light)the only idiot light that doesnt work. thanx for all your help

 

[Starship]

i have figured out the check engine light does not work but the ses light does. I figured this out by disconnecting the tps and the check engine light does not come on. if i reset the light by the scanner it shows no codes on the scanner and it shows the check engine light to be off. i think the check engine light is burnt out. as for tapping into a 5v source doesnt the ecm read off of the ground wire? So if it reads resistance off the ground it really shouldnt matter where the ref sig comes from as long as it can read the resistance on the ground wire right? and one more thing are the idiot lights replacable or not. it is (check engine light)the only idiot light that doesnt work. thanx for all your help

There's a pull-up resister inside the ECM in a series with the thermister at the IAT sensor. In order to measure the voltage drop across the IAT sensor, you need both leads. On the instrument cluster lamp, it's probably one of those bulbs the size of side markers.

 

[White98bu]

UPDATE !!!!!!! prob w/ iat is fixed ok call me a moron i had no ref sig (5v)at the plug. bared a piece of wire from the ref wire checked volts surprise 5v checked the plug 0v got different plug spliced in to harness and wow 5v stupid plug. still dont have check engine light but will check it later but scanner says no mil light. yay and iat is reading through scanner is working to spec i really want to thank you all for your help with me being a noob .

 

[Starship]

UPDATE !!!!!!! prob w/ iat is fixed ok call me a moron i had no ref sig (5v)at the plug. bared a piece of wire from the ref wire checked volts surprise 5v checked the plug 0v got different plug spliced in to harness and wow 5v stupid plug. still dont have check engine light but will check it later but scanner says no mil light. yay and iat is reading through scanner is working to spec i really want to thank you all for your help with me being a noob .

Congrats.

 

[Silver LTZ]

Glad you fixed it!