Question: Service engine Light!!
- Thread starter moedom19
- Start date
rlg
Well-known member
check the codes
Hib Halverson
Technical Writer for Internet & Print Media
The "check engine light" means there is something wrong with the engine control system.
The first thing you need to do is command the ECM to display the fault codes in its memory. There explanations of how to do this elsewhere in the CAC and in a lot of places on the Internet. If you have the factory service manual for your 90, the procedure will also be in there.
Post the fault codes.
The first thing you need to do is command the ECM to display the fault codes in its memory. There explanations of how to do this elsewhere in the CAC and in a lot of places on the Internet. If you have the factory service manual for your 90, the procedure will also be in there.
Post the fault codes.
adfac
Well-known member
My "Service Engine Soon" light on my 86 has been coming on for over a year. I've checked all the codes with no luck. Even had a mechanic check it out. He got a whole different set of codes and we still had no luck. Sometimes at 7 am when I'm heading north on the highway with the wind, the light goes on. 5 hours later around noon, I'm heading south on the same highway into the wind and the light never comes on. Car runs great. Very frustrating. Just gave up on it. I've got a 94 Suburban that also does the same thing ... and it's been that way for over 10 years. :L
I have seen this intermittent/erradic occurance on several other vehicles of various brands where no codes show up and the mechanics are left scratching their head. Many times they blame the O2 sensor. As long as the engine is runnig as usual, and no other codes show a reason for the light to come on, they just tell me to keep an eye on it.
My instincts tend to lead to Hib's post. There should be a coded reason why that light comes on. I like analytical deductions based on facts but sometimes these engines seem to develop a personality all their own and you need to learn to adapt and sometimes accept that there is something going on that the computer can not explain. Our mini van does this when we push hard on the gas to get up to highway speeds. Other times it comes on in the middle of a crusing run.
Bottom line is keep an eye on it, listen and feel what it is telling you when the science is confused.
Dig deep in the threads and keep asking questions.
Bob
My instincts tend to lead to Hib's post. There should be a coded reason why that light comes on. I like analytical deductions based on facts but sometimes these engines seem to develop a personality all their own and you need to learn to adapt and sometimes accept that there is something going on that the computer can not explain. Our mini van does this when we push hard on the gas to get up to highway speeds. Other times it comes on in the middle of a crusing run.
Bottom line is keep an eye on it, listen and feel what it is telling you when the science is confused.
Dig deep in the threads and keep asking questions.
Bob
Hib Halverson
Technical Writer for Internet & Print Media
In re, comments by "adfac": since the car is an 86, which requires a "Pin E" adapter to connect to most scan testers, there is a problem when you try and take data without that adapter. Either you'll get no data at all or you'll get erroneous data. Many consumer-grade (ie: low price) testers and even some "professional" testers do not properly support the 86-89 ECMs because of this problem.
In re: the comment to "just keep an eye on it--IMO that's very sound advice, especially if the light is coming on due to excessively lean mixture. The correct way to proceed when the light comes on at high throttle openings then goes off in normal driving is to check the ECM for "history" codes or have a tester connected during road testing.
In re: the comment to "just keep an eye on it--IMO that's very sound advice, especially if the light is coming on due to excessively lean mixture. The correct way to proceed when the light comes on at high throttle openings then goes off in normal driving is to check the ECM for "history" codes or have a tester connected during road testing.
adfac
Well-known member
- Thread starter
- #8
lefoy84
Member
rlg
Well-known member
the way I read the FSM it will flash codes 21 or 22. 21 seems to be TPS failure 22 seems to be the circuit failure.
You can get the sensor at a local parts store.At least you can here.
You can get the sensor at a local parts store.At least you can here.
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- #11
- Thread starter
- #12
moedom19
Member
The code came up as 21...
JAKE
Well-known member
Once you replace the TPS, you'll need to adjust the voltage using a digital volt meter. .54 (+/- .075) is the stock spec. I use to set mine at .62
You merely attach the DVM to the top and middle wires of the TPS harness (doesn;t matter which lead goes where), then turn the ignition key to "ON" but do not start the engine. Take your reading and adjust the voltage by rotating the sensor either up or down, as needed.
Lock down the screws while watching to be sure the voltage doesn't change, which it can do as you tighten the two screws.
Hope this helps.
Jake
West Point ROCKS!
You merely attach the DVM to the top and middle wires of the TPS harness (doesn;t matter which lead goes where), then turn the ignition key to "ON" but do not start the engine. Take your reading and adjust the voltage by rotating the sensor either up or down, as needed.
Lock down the screws while watching to be sure the voltage doesn't change, which it can do as you tighten the two screws.
Hope this helps.
Jake
West Point ROCKS!
hotshotzny
Well-known member
sounds like the gremlin i had in my 82.. car WOULD NOT RUN around a graded curve just below my house, warm engine, cold engine, full tank, empty tank it didnt matter, the car would stall and id have to start it in front of one of my biggest rival bars in the town! most times i would just coast past if i could if there were people outside smoking..... i never did figure out what the heck that was all about
hotshotzny
Well-known member
where in ny you from moedom?
- Thread starter
- #16
moedom19
Member
Long Island NY, Islandia
rlg
Well-known member
Any Luck??
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