ENGINE SERVICE SOON light

[tuononero]

I'm writing just to know if this already happened to someone of you before.

My engine check light comes up randomly. Last time it stayed on 2 days, before going to autozone for the computer checking i tried the paperclip but the result was a continue 12 12 12 - 12 12 12 -12 12 12 but when i decided to go to autozone the light disappeared.
Yesterday after 2 weeks of normal driving the light came back on.
I parked the car, left for 3 minutes, then on my way back the car didn't crank.
The battery cable had some oxidation on the terminal, after playing with them i started the car normally and the light was off......

Any ideas? 😀

Thanks

 

[paart]

I think there's a a fairly good chance that you have "fixed" the problem. The only way be sure is to drive the car.

 

[tuononero]

Sadly not.
Today i drove for about 90 miles (45 + 45) and the light came up like 3 or 4 times. When i turn the engine off and i start it up again the light goes away, if i drive it in the town it stays off, when i drive it a little longer it comes up grrrrrrrrr

 

[tuononero]

Today i took again the RM for a long trip and the light came back on, so i drove to o'reilly and left the car on so they could check it, but the guy plugged the computer in and his computer didn't turn on, so he turned the car off and back on (light disappeared) but the computer still off, so he said "your car is not supplying power to the computer". Any idea? A fuse or the name of a saint to pray?

Thanks

 

[tuononero]

I just checked the plug with a multimeter, there is power... what's going on???

 

[buickwagon]

Unless it's a 1996, it won't supply power to his computer -- that's an OBD II thing. OBD I, used up to 1995 required the scan tool to have it's own power supply. Most used the lighter socket.

There are some minor errors that self-reset without a key cycle, but they should still store a code in memory. If there's truly nothing in memory, it could be the following:

Electrical system interference caused by a defective relay, ECM driven solenoid, or switch. They can cause a sharp electrical surge. Normally, the problem will occur when the faulty component is operated.

Improper installation of electrical options, such as lights, radios, etc.

EST wires should be routed away from spark plug wires, ignition system components and alternator. Wir for circuit 453 from ECM to ignition system should be a good ground.

Ignition secondary shorted to ground.

Circuit 419 ("Service Engine Soon" light) or circuit 451 (diagnostic "test" terminal) intermittently shorted to ground.

ECM power grounds.

Loss of diagnostic code memory. To check this, disconnect the Throttle position sensor and idle the engine until the SES light comes on. A code 22 should be stored when the ignition is turned off for at least 10 seconds. If not, the ECM is faulty.

 

[tuononero]

Thank you for the answer, of course a lot of stuff to check and i will one by one.

But digging on google i found a website explaining the most common causes of check light. One of them was a failure in the gas cap. I actually don't have a gas cap. Could it be my problem??? That would explain why it doesn't come on when i start it up.

 

[buickwagon]

Nope, that's an OBD II thing. Your 93 is pretty primitive, with only 18 possible codes (19 if you count the "all's well" code 12).

13 O2 sensor open
14 Coolant Temperature sensor high temp
15 CTS low temp
21 Throttle Position sensor high voltage
22 TPS low voltage
23 Intake Air Temp low temp
24 Vehicle speed sensor
25 IAT high temp
32 Exhaust Gas Recurculation
33 Manifold Absolute Pressure voltage high (pressure low)
34 MAP voltage low (pressure high)
42 Electronic Spark Timing
43 Electronic Spark Control
44 O2 lean
45 02 rich
51 PROM error
54 Fuel pump low voltage
55 ECM error

Note that there can be several reasons behind any code -- it's just a starting point for the diagnosis. EG: if you have a code 45, the problem might be a faulty 02 sensor, ignition misfire, excessive fuel pressure, leaking injector body, wiring fault, etc. etc. The factory service manual is invaluable for tracking down the real problem.

 

[tuononero]

Ok, that is a pretty cool answer, i love it. But why those codes are not memorized? Why doesn't it stay on so that i can go somewhere and check it? Should i just go somewhere like i did today and leave the engine on plugging the computer in directly and make a read? Can't i do that with the paperclip method while the engine is running?

 

[Griswold]

I feel your pain. I had a 91 Caprice that threw check engine lights since the day it was new. It was in to the dealer over 20 times in 20K km and they couldn't figure it out. One time they gave it back to me with the infamous "no fault found". I started it and the light came on. Left it there and got it back with no fault found, this time with the light out. Went to arbitration and GM was ordered to buy it back.

 

[buickwagon]

Yes, any of those codes should be memorized -- until the battery is disconnected or fuse removed. I believe you can still use the paperclip method on a 93. It should flash "12" three times (confirms the system is working), then flash the first stored code 3 times, then the next stored code 3 times, and so on. Once all codes have flashed, it repeats the sequence starting with 12 (x 3) again. So if it just repeats 12 over and over ad infinitum then there are no stored codes. See post #6.

Don't start the car or insert the paperclip with the engine running. The paperclip should be inserted, then turn the key to "On" but don't start it.

A scan tool can be used with the engine running, and in fact a scan tool can display not only error codes, but also all the actual live sensor values while the engine is running. The problem is finding someone who still has a GM-capable OBD I scan tool. OTOH, that means they are now going cheap when you can find a good one on eBay.

 

[tuononero]

I feel your pain. I had a 91 Caprice that threw check engine lights since the day it was new. It was in to the dealer over 20 times in 20K km and they couldn't figure it out. One time they gave it back to me with the infamous "no fault found". I started it and the light came on. Left it there and got it back with no fault found, this time with the light out. Went to arbitration and GM was ordered to buy it back.

Bummer, and maybe it was a stupid thing... we will never know... 😀

Buickwagon... it happened that i turned the car on with the paperclip inserted... 😱 the light started to flash code 1 (- - - - - - -)infinitely.
Hope nothing happened to the ecm doing this 🙁

 

[buickwagon]

IIRC, you won't damage anything by starting the car, but the ECM will enter a fail-safe mode ("Road Test") and ignore most inputs.

You say the light flashes "1" continuously? Not "12"? Is that a typo? Is that Key On Engine Running (KOER) or Key On Engine Off (KOEO)? If it flashes "12" continuously, there are no stored codes. If it's flashing "1" continuously, then I have no idea what's going on -- all codes should be 2 digits, so that would be "11", but there is no code 11 that I am aware of.

If the light flashes "12" continuously, then there are no codes stored. If no codes are stored, the SES light has been on while driving, and the battery has not been disconnected or the fuse pulled since the light came on, then see post #6.

 

[tuononero]

Ok maybe i made some confusion.

KOEO with paperclip = Code 12 (no codes stored)
KOER with paperclip = CODE 1 (sounds strange but i can post a video), but as soon as i take the paperclip off (engine still running) the light turns off.

I think you swapped the KOEO and KOER but i gotcha.

I'll keep you posted on the tries.

 

[buickwagon]

Ok maybe i made some confusion.

KOEO with paperclip = Code 12 (no codes stored)
KOER with paperclip = CODE 1 (sounds strange but i can post a video), but as soon as i take the paperclip off (engine still running) the light turns off.

I think you swapped the KOEO and KOER but i gotcha.

I'll keep you posted on the tries.

Yup, I goofed. All fixed now.

Ok, let's ignore the KOER results as meaningless. The important bit is you get a code 12 KOEO, that repeats forever with no other codes stored in memory. So, off to post 6 with you!

 

[MichaelSchmu]

So I have a 93 Buick Roadmaster and just the other day it was driving just fine and now it want start the Engine service soon light came on i cranks but it wont turn over

 

[HotZ28]

So I have a 93 Buick Roadmaster and just the other day it was driving just fine and now it want start the Engine service soon light came on i cranks but it wont turn over

Welcome to the forums! Have you checked spark to the plugs & fuel pressure? This is an 7-yr old thread and it would be better to start a new thread with this problem. BTW, what was the code?

 

[G-98628]

Please need help figuring out each number on each line of the oil psi gauge . 93 roadmaster