Service Engine Soon - warning light - Page 2 - PeachParts Mercedes-Benz Forum

Mölyapina · #16 01-08-2015, 11:13 PM

Here ya go, cmac:

How to read older GM OBD diagnostic codes for free

That works for all GMs made 1993 and before and with some 1994 cars.

cmac2012 · #17 01-09-2015, 12:29 AM

Quote:

Originally Posted by Skippy

Agreed. Pulling codes tends to be one of my first pieces of advice for anything from which codes can be pulled, or as an electrical engineer friend from college used to say, "Ask it where it hurts."

Quote:

Originally Posted by kerry

89 is OBDI I think. You should be able to jump a couple of the terminals on the connector and get the code from the number of flashes from the Service Engine light.

Good advice. I was negligent in my research on this. I had looked in the Haynes manual and did a Google search but I couldn't have been too thorough on either as I found it in the manual, looking a bit closer. In the index under 'computer' was included 'trouble codes.' They show the terminal that you need to ground, with key on, to start the process. From the blinking I get the info that my O2 sensor may be bad or perhaps the wiring has degraded. Should look at the throttle position sensor as well perhaps.

I should have researched this a bit more closely up front but my public shaming here at least moved me to research it at last.

aklim · #18 01-09-2015, 12:44 AM

Quote:

Originally Posted by cmac2012

From the blinking I get the info that my O2 sensor may be bad or perhaps the wiring has degraded. Should look at the throttle position sensor as well perhaps.

I should have researched this a bit more closely up front but my public shaming here at least moved me to research it at last.

Was the O2 sensor lazy or just died? Did you probe the output? I suspect that it was a single wire not the 4 wire sensors today. Are you sure that the output is accurate? It has to achieve certain temperatures before it is reliable. If you want you can tap into the feed and see what the DVOM sees. That way you know what voltage you get and if the ECM sees it different, there is a wiring problem. GET A SCANNER.

TPS. you are going to need a DVOM. 3 wires. 1 ground, 1 5V reference and one output from the sensor. It must be smooth when you accelerate

JB3 · #19 01-09-2015, 12:47 AM

Are there any drivability issues to this van besides the light being on?

cmac2012 · #20 01-09-2015, 12:59 AM

^ Good question. This van is pretty good. Had nice, extra-deluxe Michelins all around, spare even, when I bought it at 129K. Seems the POs were not cheapskates. Has always run well and still does. The one thing I've noticed in the last few weeks (I drive it maybe once a week) is that it will sometimes stall at slow speed, say while parallel parking.

I only get about 13 mpg (one of those long vans) so something like a bad O2 sensor might not stop its running but could lower efficiency. I think.

cmac2012 · #21 01-09-2015, 01:05 AM

Quote:

Originally Posted by aklim

Was the O2 sensor lazy or just died? Did you probe the output? I suspect that it was a single wire not the 4 wire sensors today. Are you sure that the output is accurate? It has to achieve certain temperatures before it is reliable. If you want you can tap into the feed and see what the DVOM sees. That way you know what voltage you get and if the ECM sees it different, there is a wiring problem. GET A SCANNER.

TPS. you are going to need a DVOM. 3 wires. 1 ground, 1 5V reference and one output from the sensor. It must be smooth when you accelerate

Not sure, I just pulled the codes tonight. I thought about waiting until I fixed it before I posted but as the central question, i.e. - can trouble codes be pulled - had already been answered and I demonstrated it to myself. Seemed to be less than polite to then have people continue to answer the question when I'd already been assured of the answer.

But these are good tips you bring up.

JB3 · #22 01-09-2015, 01:09 AM

Quote:

Originally Posted by cmac2012

^ Good question. This van is pretty good. Had nice, extra-deluxe Michelins all around, spare even, when I bought it at 129K. Seems the POs were not cheapskates. Has always run well and still does. The one thing I've noticed in the last few weeks (I drive it maybe once a week) is that it will sometimes stall at slow speed, say while parallel parking.

Before i settled on an express i really wanted a G series van. I find them attractive as far as vans go, but they are next to impossible to find without major rust in these parts. You should post a pic of it

I missed out on a 3 speed column shift 79. Still kicking myself

Skippy · #23 01-09-2015, 05:09 AM

Quote:

Originally Posted by cmac2012

^ Good question. This van is pretty good. Had nice, extra-deluxe Michelins all around, spare even, when I bought it at 129K. Seems the POs were not cheapskates. Has always run well and still does. The one thing I've noticed in the last few weeks (I drive it maybe once a week) is that it will sometimes stall at slow speed, say while parallel parking.

I only get about 13 mpg (one of those long vans) so something like a bad O2 sensor might not stop its running but could lower efficiency. I think.

O2 sensors usually degrade slowly over time and tend to bring fuel efficiency down when they get near the end of their service lives. The stalling sounds like something different, like maybe the TPS you mentioned.

aklim · #24 01-09-2015, 07:26 AM

Quote:

Originally Posted by Skippy

O2 sensors usually degrade slowly over time and tend to bring fuel efficiency down when they get near the end of their service lives. The stalling sounds like something different, like maybe the TPS you mentioned.

Kinda why I like scanner data. I would have the engine off but key in run, see what happens when I slowly depress the pedal. Voltage should go up smoothly. If it skips or spikes, TPS is bad. That has more effective influence on stalling, I think6,than O2 sensor. Could be dirty injectors.

DieselPaul · #25 01-09-2015, 08:59 AM

If you've never replaced the O2, and you're skeptical of it, they are only $11 on rock auto for an NGK or a Bosch. I'd just replace it. Even if its just tired, not totally shot, you may enjoy some better fuel economy.

kerry · #26 01-09-2015, 09:19 AM

Quote:

Originally Posted by aklim

Kinda why I like scanner data. I would have the engine off but key in run, see what happens when I slowly depress the pedal. Voltage should go up smoothly. If it skips or spikes, TPS is bad. That has more effective influence on stalling, I think6,than O2 sensor. Could be dirty injectors.

I don't think there are any scanners available which will provide that data. I have a 93 GMC 6.5 and all the forums indicate that the only way to get any info is from the original GM software program. There are aftermarket software programs available for 94+ GM OBDI vehicles.

MY TPS wasn't working right on my 93. (It sends a signal to the transmission control module). I discovered that the problem was a poor connection at the 'off' position. It always sits in that position and the connection deteriorates over time. I simply turned the adjustment on the TPS so the 'off' position was slightly different and it now works fine. This is a common problem on the 93 GM diesel truck TPS. Not sure about 89 gas models.

aklim · #27 01-09-2015, 10:23 AM

Quote:

Originally Posted by kerry

I don't think there are any scanners available which will provide that data. I have a 93 GMC 6.5 and all the forums indicate that the only way to get any info is from the original GM software program. There are aftermarket software programs available for 94+ GM OBDI vehicles.

MY TPS wasn't working right on my 93. (It sends a signal to the transmission control module). I discovered that the problem was a poor connection at the 'off' position. It always sits in that position and the connection deteriorates over time. I simply turned the adjustment on the TPS so the 'off' position was slightly different and it now works fine. This is a common problem on the 93 GM diesel truck TPS. Not sure about 89 gas models.

I beg to differ. I have such a unit in my garage. You can buy the scanners that are OBD2 or OBD2 and OBD1. I think Autozone has them so you can borrow them to scan.

BAVBMW · #28 01-09-2015, 11:35 AM

There are certainly scanners to communicate with early GM systems, they will give access to live data, though the data transfer rates may be to slow to capture everything you'd like to see.

You say an oxygen sensor code... My memory has grown hazy after not having worked on American cars in over a decade, but I think the main codes that mention the oxygen sensor are 13, 44, and 45. Of those I seem to remember that 13 was something along the lines of an open circuit, and 44 an 45 were rich/lean, or vice-versa. The codes saying rich/lean are usually not an oxygen sensor problem, but rather the oxygen sensor correctly reporting that the mixture is off.

What else can you tell us about the vehicle? Carb? TBI?

MV

cmac2012 · #29 01-09-2015, 01:12 PM

Quote:

Originally Posted by DieselPaul

If you've never replaced the O2, and you're skeptical of it, they are only $11 on rock auto for an NGK or a Bosch. I'd just replace it. Even if its just tired, not totally shot, you may enjoy some better fuel economy.

That was my thought. I wouldn't have thought they were quite that cheap but I'm not complaining. I'll check the wires also.

cmac2012 · #30 01-09-2015, 01:19 PM

Quote:

Originally Posted by BAVBMW

There are certainly scanners to communicate with early GM systems, they will give access to live data, though the data transfer rates may be to slow to capture everything you'd like to see.

You say an oxygen sensor code... My memory has grown hazy after not having worked on American cars in over a decade, but I think the main codes that mention the oxygen sensor are 13, 44, and 45. Of those I seem to remember that 13 was something along the lines of an open circuit, and 44 an 45 were rich/lean, or vice-versa. The codes saying rich/lean are usually not an oxygen sensor problem, but rather the oxygen sensor correctly reporting that the mixture is off.

What else can you tell us about the vehicle? Carb? TBI?

MV

I haven't been into the engine much but it sure looks like a carb. I'll pull the cover off and look more closely tonight. Not sure if the TBIs look much different at a quick glance.

The two codes I got were 13 and 42. 13 described as 'O2 sensor circuit' and 42 as 'electronic spark timing.' Not sure about the latter as they refer to not starting with this issue.