Cancel service engine soon light

How do you cancel the service engine soon light on a 94 LeSabre ?.

Hello

I did a search on the internet and found this link for reading the codes: http://www.obd-codes.com/faq/read-gm-2-digit-obd-codes-free.php

To reset follow this link: http://www.obd-codes.com/faq/reset_obd_codes.php

Regards

Dan

Hello

I did a search on the internet and found this link for reading the codes: http://www.obd-codes.com/faq/read-gm-2-digit-obd-codes-free.php

Regards

Dan
Let’s not confuse the 12-pin OBDI connector shown in the link above, with the 16-pin OBDII ALDL (shown below) and used in 94-95 LeSabre (OBD1.5) The procedure described in the link will not work on these cars! :sorry:


http://img297.imageshack.us/img297/9954/obd11pinoutzp6.jpg

Hi
Thank you for your response, I had a guy do the scan today and it said TPS (Throttle position sensor) He would have to order it $85.00 !??, Does that sound right to you ?, The one he pointed to on my car is mounted on the left side of the throttle body under another sensor, so close to Exhaust crossover pipe, I don't know if there is room to get a tool on the mounting bolts/screws ?. I think the scanner said Low voltage and it was the only code showing in history or current, When he tried to clear it, it said vehicle not responding, I wonder if that is because you have to change it first ?.
Is there any chance it can just be cleaned and reinstalled ?, or find a good used one in the wrecking yard ?, I have no experience with these, So I would greatly appreciate your opinion.
Thank You Rick

He would have to order it $85.00 !??, Does that sound right to you ?, The one he pointed to on my car is mounted on the left side of the throttle body under another sensor, so close to Exhaust crossover pipe, I don't know if there is room to get a tool on the mounting bolts/screws ?.

The TPS runs about $85.00 at most part suppliers. It sound like he pointed to the correct sensor, and normally, the use an offset screw driver is required to remove these.

I think the scanner said Low voltage and it was the only code showing in history or current, When he tried to clear it, it said vehicle not responding, I wonder if that is because you have to change it first ?

No, you should be able to clear the code and see if it comes back. Something is funky here! If the scanner was able to read the code for the TPS low voltage to begin with, it should be able to continue reading data. TPS low voltage does not necessarily mean that the TPS is at fault! This could be a number of problems, including grounds, reference voltage, or even the PCM! It sounds like your mechanic likes to replace parts based on what the DTC’s are! This is not a good basic diagnostic procedure!

Is there any chance it can just be cleaned and reinstalled ?, or find a good used one in the wrecking yard ?,

There is no way to clean the TPS & reinstall! A used one may be good, or it may not! Be cautious when using JY electrical parts, you never know how long they have been sitting in the JY subjected to condensation from harsh environments! (Most of the time, with the hood off)

The TPS runs about $85.00 at most part suppliers. It sound like he pointed to the correct sensor, and normally, the use an offset screw driver is required to remove these.



No, you should be able to clear the code and see if it comes back. Something is funky here! If the scanner was able to read the code for the TPS low voltage to begin with, it should be able to continue reading data. TPS low voltage does not necessarily mean that the TPS is at fault! This could be a number of problems, including grounds, reference voltage, or even the PCM! It sounds like your mechanic likes to replace parts based on what the DTC’s are! This is not a good basic diagnostic procedure!



There is no way to clean the TPS & reinstall! A used one may be good, or it may not! Be cautious when using JY electrical parts, you never know how long they have been sitting in the JY subjected to condensation from harsh environments! (Most of the time, with the hood off)
Thanks a Lot for your insight, I will check out the grounds tomorrow(depending on the weather) so far I haven't ordered anything, one symptom I never mentioned before is the last couple days it stumbles pretty bad on an uphill pool.
Rick

one symptom I never mentioned before is the last couple days it stumbles pretty bad on an uphill pool.Rick
When is the last time you replaced the plugs, wires, fuel filter and checked the coils resistance? How many miles on this car?

There is no way to clean the TPS & reinstall!

Normally I'd defer to your expertise, but actually, it is possible:

http://72.19.213.157/files/TPSRepair.jpg

I wouldn't advise it, however, unless you have the facilities for miniature assembly and repair. The bifurcated contacts of the potentiometer wipers are very sensitive and fragile.

Just like repairing you own MAF sensor:

http://72.19.213.157/files/MAFDisassembly04.jpg

I agree completely that the DTC (error code) does not necessarily mean that the particular item(s) described in the error is faulty. The TPS is relatively easy to diagnose with only a voltmeter/ohmmeter. As previously advised, verify the presence of a correct reference voltage at the sensor, and measure the range of signal from the sensor to the PCM (right at the sensor). The gray wire should be + voltage, black is ground, and the dark blue wire is the signal.

Nice show and tell Jeff, however, I agree with Bo in this case and most cases concerning TPS issues. Disassembly is not recommended to the average car owner or DIY type unless you really know what you are doing. :nono:

To the OP just check the TPS input and output including linearity as you move the throttle before removing it and/or tearing it apart. Autozone Repair Info has an excellent guide you can use. See link below.

Click here (http://www.autozone.com/az/cds/en_us/0900823d/80/17/8f/36/0900823d80178f36/repairInfoPages.htm)

Nice show and tell Jeff, however, I agree with Bo in this case and most cases concerning TPS issues. Disassembly is not recommended to the average car owner or DIY type unless you really know what you are doing. :nono:

To the OP just check the TPS input and output including linearity as you move the throttle before removing it and/or tearing it apart. Autozone Repair Info has an excellent guide you can use. See link below.

Click here (http://www.autozone.com/az/cds/en_us/0900823d/80/17/8f/36/0900823d80178f36/repairInfoPages.htm)
Thank you very much for the link to autozone, I printed it out and will try to follow it, You guys are better than the repair manuals,
Rick

I found my Cables pretty corroded on my 94 LeSabre and the plugged were due to be changed, cleaned the cables and put new plugs in hoping the Service engine soon would reset, It didn't, (The Battery was disconnected about 1 hour)

Now I am back to the TPS, The code was low voltage at TPS, trying to check it with an ohmeter, but not sure what the reading should be at the 2K setting it reads 1.371 and by 1/3 throttle it's down to one with no further reading all the way to full throttle, How sensitive should it be, I don't really understand a lot about OHMs.

I want to check the voltage but not sure how to hook up the leads, I printed out the link at Autozone on the TPS but it's kinda vague on the hookup.
This 94 has 246,000 miles and always ran perfect.
With the TPS plugged in I would have to pierce the wires to check the voltage wouldn't I ?.
Any help greatly appreciated.
Rick

Please try to keep your threads of the same subject combined. Your new thread, is now merged with your previous thread on the same subject!

Please try to keep your threads of the same subject combined. Your new thread, is now merged with your previous thread on the same subject!
Sorry

One more thing I noticed yesterday while test driving, No kickdown at any speed, I rarely ever use it, so Don't know if it's new symptom or not, The car run's really strong but the service engine soon light is still on.

I put the ohmeter between the black post and the blue post and got a full range of readings throughout the movement of the throttle, So I guess that means it's not the TPS ?.

One more thing I noticed yesterday while test driving, No kickdown at any speed, I rarely ever use it, so Don't know if it's new symptom or not, The car run's really strong but the service engine soon light is still on.

I put the ohmeter between the black post and the blue post and got a full range of readings throughout the movement of the throttle, So I guess that means it's not the TPS ?.
In order for us to help here, it is important that you tell us what the TPS voltage readings are @ closed throttle & WOT. When you say; “I put the ohmeter between the black post and the blue post and got a full range of readings throughout the movement of the throttle”, does not tell us much. This is not enough information for anyone to tell if the TPS is good, or bad!

The TPS is simply a potentiometer used to vary voltage. The best way to check the voltage is with a scanner, but if you do not have access to one, you can use a DVOM. You can probe the terminal with a paper clip to check voltage. The TPS WHITE wire, is the PCM reference signal and should measure 5.0v with ignition on. (Engine does not need to be running) The BLUE wire will show variable voltage from a closed TB position, usually .45v, up to WOT, where it should measure between 4.0v to 4.2v max. Of course, the BLACK wire is ground.

In addition, to verify the voltage that the PCM is using, you must use a scanner! I have seen several throttle position sensors check fine with the DVOM; however, the PCM was altering the reading! In these cases, the reference voltage from the PCM was correct (.5v) and the TPS output was correct, but the PCM had skewed voltage reading and internal failure. When this condition exist, the PCM will need replacing.

Some of the problems you mention here; “No kickdown at any speed”, seem to indicate PCM malfunction. The 94-95 PCM’s are notorious for creating unexplained problems. The #1 cause of PCM failure is voltage spikes! Voltage spikes begin to happen with corroded battery cables, or failing internal voltage regulator in the alternator. I have seen several PCM failures, simply due to removing the positive (+) battery cable before the negative cable(-).

Thank you for the detailed reply, Very much.

Sorry about not giving the details on the Ohms test, I had outlined it yesterday when I mistakenly posted it as a new post, and you pointed out my error and moved it, so naturally I thought you were familiar with the previous
post.

When I checked the TPS with the Ohmeter yesterday it was unplugged so the PCM would not have any effect on the reading, Basically the ohms test just shows you have continuity right ?, But the voltage test shows you have functionality of the TPS, if I understand you right .

The TPS plug on mine seems to be sealed on the backside of the plug with no access to any metal, that's why so far I haven't checked the voltage, I don't want to break the plug. Thanks again Rick

Basically the ohms test just shows you have continuity right ?, But the voltage test shows you have functionality of the TPS, if I understand you right .

The TPS plug on mine seems to be sealed on the backside of the plug with no access to any metal, that's why so far I haven't checked the voltage, I don't want to break the plug. Thanks again Rick

Actually, you are only checking ohms-resistance, not "continuity". The volt test will reveal voltage, that is what you (and us) need to know. You can probe the backside of the terminal where the wires go in with a needle, or paperclip. It looks sealed, however, it is actually a compressed insulation (silicone). I normally attach my DMM probe (+) to the needle with an alligator clip after probing the terminal, and the negative probe (-) to an engine ground with another alligator clip. This method will give you good contact points and you don’t have to worry about holding the probes with your hands. Try this and let us know the Volt reading you find. :)

Thank you once again, I just returned from auto parts, Had it scanned, it still says TPS and the scanner won't cancel the light, it say's vehicle not responding, when I got home I put my DVM on the Batt, engine off got 12 3, Started the car turned everything on and got 13.7, Don't know how critical that is, I thought it would be about 14.25 ?, Thank you for sharing your knowledge about the TPS plug insulation, that will be my next move and I will post the results.
How much Battery/Alternater voltage fluctuation does it take to be considered a voltage spike ?.
Rick
PS
The scanner at this parts store does not read voltage, but it's a freebie so I can't complain.

Had it scanned, it still says TPS and the scanner won't cancel the light, it say's vehicle not responding,
The scanner at this parts store does not read voltage, but it's a freebie so I can't complain.
If the scanner at the auto parts store says "vehicle not resopnding & it will not cancel the light" how did it read a TPS fault? :screwy: Something is wrong here! :uhoh:

That is a good question ?.:runaround:

Post the TPS voltage test results. A faulty TPS will result in the transmission NOT downshifting under load, since the PCM requires throttle position input to control shifting. Without it, it is strictly and engine RPM/VSS calculation.

I suspect the scanner being used is not fully bidirectional. You'll need a Vetronix Tech II, Matco Determinator, or SnapOn MT2500.

Thanks I will check the voltage ASAP, if it ever stops rainng.
Rick

You should consider purchasing a full function scanner capable of reading live-data on 94-95 PCM's. Click here (http://cgi.ebay.com/ebaymotors/ACTRON-9150-SUPER-Auto-Scanner-Kit-OBD-1-2-CP9150_W0QQitemZ170189171341QQcmdZViewItem?hash=it em170189171341) for a look at the Actron CP9150 at a fair price. This could pay for itself the first time you use it! Not advertising this paticular one, just offering alternatives.

Boy if I were 20 years younger, that would be awfully tempting, But my 1930 Model A 5 window coupe currently demands all my attention, that is until the old buick has a problem, But thanks for the thought.
Rick

Hi
I just checked the voltage on my TPS it is as follows
Unplugged key on engine off 5.1 volts at the plug.

Plugged in, key on, not running + lead to center (blue wire) - black lead to engine ground.
Idle position =.10
1/4 throttle = .18
1/2 throttle = .23
3/4 throttle = .26
WOT = .47
As close as I can judge the different positions, it does seem to change value's smoothly and consistently.

My Battery shows 12.3 No load engine off
full load engine idling shows 14.5 when A/C kicks in it drops to 13.9
So I am thinking it's probably the PCM, but I will await you guys interpretation of these readings.
It is a 94 LeSabre 3.8 with an L in the Vin which I think indicates the engine specs ?.
Rick

Additional question
If my problem is in the PCM, Do I need to replace the ECM which has the Prom in it, I am confused, on what to be looking for, I know the ECM will fit many cars but the PCM is specific to one engine and fits into the Prom ?? ! .

I hope I am doing this right, I am not responding just asking another question, anyway I talked to a guy today that doe's this stuff and he advised me to start with the TPS, He said to reset the light on this car you have to discharge the circuit by touching the ground cable (disconnected of course) to the positive cable for a couple seconds then reconnect it and the code would be gone, it was, for about 5 seconds then came back on, he seemed to think the TPS was most likely the problem, so I guess its an $80.00 gamble, if that don't work then it's a $50.00 gamble with a junkyard ECM, mine is the type with a removable PROM and I can simply plug my Prom into another ECM and be good to go ?, Before I done that I thought I would install the TPS and see if that was the problem, right now the engine is too hot to get at the screws holding the TPS onto the throttle body, So I am contemplating taking the throttle body off for better access to the screws, but hesitated because it looks like I have one of those infamous plastic upper plenims that the throttle body bolts too and I am leary of breaking a sealed joint there, so I thought maybe some of you guys might be able to tell/advise the best was to proceed, I will exhaust all possible means to loosen those screws first, but if I can't what am I looking at to reseal the throttle body ?, I have owned the car since 95 and none of this stuff has ever been off before.
Rick

Plugged in, key on, not running + lead to center (blue wire) - black lead to engine ground.
Idle position =.10
1/4 throttle = .18
1/2 throttle = .23
3/4 throttle = .26
WOT = .47 More than likely you have the decimal point off on all of these readings. Move the decimal point over one number to the right and that would be more likely correct. Even with the decimal point moved, these readings are way out of kilter. Idle (closed throttle) should be less than .5v and WOT should not be more than 4.0v to 4.2v. You have a problem here with TPS voltage. Has anyone tried to adjust the voltage? You can adjust the voltage a small amount (+ or - .2v) but not .5v, without removing the metal spacers inside of the screw holes. Since the WOT voltage is way high, as well as the closed throttle, try loosening the TPS screws and see how much you can change the setting. Remember, you want less than .5v (.45 would be ideal) closed throttle and about 4.0v to 4.2 max @ WOT.

Think of the ECM/PCM as one unit. The ECM used a “prom” until 1996 when the full conversion to OBDII and PCM control took place. Your ECM does have a “prom” that will need to removed from your old ECM & installed into the new ECM. If you go that route, we can give details on this change. In conclusion, you should try to get the TPS voltage within normal operating parameters and then post back with your findings.

EDIT: Anything over .65v on the TPS @ closed throttle will set a CES light. Let's not condemn the TPS just yet. This could very well be an ECM problem!

In case you do need an ECM here is the ID number of the ECM and prom:
Part #16183247 LeSabre '94-95 Elec Cont Module (ECM); (6-231, 3.8L)
Application: 1994-95 3.8 V6 SFI “L” L27
1995 3.8 V6 SFI “K” L36
1994-95 3.8 V6 SFI supercharged “1” L67
1994-95 truck 3.8 V6 SFI “L” L27
MEMCAL IDs: “L”: BMYU, …
“1”: … “K”: …
EPROM type: 27C512

Just to clarify what the "Metal Spacers" or bushings look like, here is a pic:
http://img170.imageshack.us/img170/6256/tps94us9.jpg

$80 for a TPS? If you're not even certain the TPS is at fault, I wouldn't drop $80 on a hunch.

Measure the reference voltage to the TPS, between the gray and black wires. Then measure the resistance from the black wire to a good ground.

Thanks I will doublecheck those readings after dinner and let you know, I was hoping you would elaborate about removing the throttle body, If the TPS is bad, I see no way to remove the screws holding it on the throttle body, it's too close to the exhaust crossover and thermostat housing, to get a screwdriver on it, Thanks for all your help.Rick

I was hoping you would elaborate about removing the throttle body, If the TPS is bad, I see no way to remove the screws holding it on the throttle body, it's too close to the exhaust crossover and thermostat housing, to get a screwdriver on it, Thanks for all your help.Rick As mentioned earlier, an offset screwdriver may be needed here. The last TPS I changed on a 94, I simply used a long flex shaft screwdriver. I never considered removing the throttle body, too much work for a little job like this! :evillol:

BTW, don't forget to loosen the screws a little bit first and see if you can rock the TPS clockwise-counterclockwise to adjust the voltage reading!

I don’t normally recommend buying AZ parts, but if push comes to shove here, you might want to consider buying the Duralast brand TPS at AutoZone for $52.99. It comes with a 2-year warranty. If it fails within those two years, take it back for a freebie. Or, as a friend of mine does, even if it is still working fine after 1 yr 11 mo. take if off and return it for a new one! :devilsign:

Believe me I would rather just use an offset screwdriver, I have tried everything in my toolbox and so far nothing has worked !.

I don't have a clue how I misread this earlier

Plugged in, key on, not running + lead to center (blue wire) - black lead to engine ground.
tonight on the 20v scale it say's

Idle position = 0.03
1/4 throttle = 0.07
1/2 throttle = 0.08
3/4 throttle = 0.10
WOT = 0.18

If I understand correctly, The reference voltage between the gray and black wires is, it bounces between 4.8 & 5.02
The resistance from the black wire to ground is 0
Sorry to be soo dense about this, but I am not at all sure I understand what you are saying. But thanks for chiming in I need all the help I can get.
Rick

tonight on the 20v scale it say's

Idle position = 0.03
1/4 throttle = 0.07
1/2 throttle = 0.08
3/4 throttle = 0.10
WOT = 0.18
What kind of meter are you using? This reading is all together different from your previous reading even with the decimals misplaced! (Could explain a bad TPS, but I doubt it)

It's a Velleman DVM 850DL new last year.
Sorry but I misread your post on 2/2 which said PCM reference and should measure 5.v, I thought that meant 5 volts, this morning with the TPS unplugged jusy measuring the voltage to the TPS it was 5.1 volts.

then I plugged it in and moved the probe to the center (blue wire)tonights readings were as follows.
Idle 0.03
1/4 0.07
1/2 0.08
3/4 0.10
WOT 0.18
So if I am reading this right the voltage is too low ?.
Rick
PS
I done it several times and it was pretty consistent

It's a Velleman DVM 850DL new last year.
Sorry but I misread your post on 2/2 which said PCM reference and should measure 5.v, I thought that meant 5 volts, this morning with the TPS unplugged jusy measuring the voltage to the TPS it was 5.1 volts.
You can probe the terminal with a paper clip to check voltage. The TPS WHITE wire, is the PCM reference signal and should measure 5.0v with ignition on. (Engine does not need to be running) The BLUE wire will show variable voltage from a closed TB position, usually .45v, up to WOT, where it should measure between 4.0v to 4.2v max. Of course, the BLACK wire is ground.
then I plugged it in and moved the probe to the center (blue wire)tonights readings were as follows.
Idle 0.03
1/4 0.07
1/2 0.08
3/4 0.10
WOT 0.18
So if I am reading this right the voltage is too low ?.
Your reference voltage looks good! The variable readings from the blue wire are not good! If this is the correct readings, you do need a TPS. In addition, the ECM uses TPS voltage to control fuel curves, timing, and transmission shift points, to name a few. Try a new TPS, you might like it! :grinyes:

Thanks to all that tried to help, I ended up having to take it to the shop, For the first time in my life I did not have a tool to get the throttle body off, there's a little bracket bolted to the bellhousing, that has to come off first and no universal socket I have could get on it, it was either remove the front exhaust manifold with the crossover or take it in to the shop, I took it in, of course I could not wtch them work but i could hear the air impact they used on those 2 bolts, They had to remove the throttle body to get the TPS off ( I guess there is locktite on the mounting screws of the TPS) Just think if they had used hex headed screws there none of this would have been necessary unless the screws broke off flush and you had to drill them out of the throttle body, It's a bitter lesson and cost $195.58 for labor +TB gasket, plus the TPS for $80.48 But it's done and the ECM is apparently OK, My Passing gear and Cruise control is working again, If I had it to do over I would cut the TPS off with my Dremel and replace the screws, Don't know if I would have replaced that bracket that covers the back Throttle body bolt or not, I sur don't see the need for it at first glance ??.
Thanks again.
Rick