vazbmw
vazbmw HalfDork
1/3/20 1:39 p.m.

Here the scenario -- which I have not seen before. The car: Volvo 850 Turbo
 

1. previous own had check engine light removed

2. I put the bulb back in

3. When you start, the car the light goes off as normal

4. Car runs

5. Then about 2 seconds later the light comes back on on stays on

6. There are no codes. The Volvo OBDII has an under-hood diagnostic to access codes (no codes) There is also and ODBII port that you can pull basic engine codes from. There are no codes from either.

What could be causing a seemly error-free check  engine light?

 

thanks for any insights

-Vaz

Run_Away
Run_Away Dork
1/3/20 1:49 p.m.

If you hit clear codes on your scanner, does the light go out?

You may need a scan tool with more capability to retrieve the code.

Streetwiseguy
Streetwiseguy MegaDork
1/3/20 1:56 p.m.

95 or older?  Plugging the wire into hole A2 (EFI), or A6(ign), or both? One may not have a connector.  As long as it has the flash code unit under the hood, the obd port is kinda useless.

vazbmw
vazbmw HalfDork
1/3/20 2:00 p.m.

In reply to Streetwiseguy :

I have done the diagnostic on the under-hood and the obdII. It's a 1994. Jumper in A2. Code of no code given 111

vazbmw
vazbmw HalfDork
1/3/20 2:07 p.m.

In reply to Run_Away :

no. Clearing codes does nothing. I have cleared codes via scanned and via the under hood diagnostic (but there is nothing to clear, so it doesn't go through the clear procedure underhood) 

 

the Volvo OBDI under hood diagnostic provides all codes, since this is not a true ODBII car. Not sure if another scanner will pull additional codes, if pulling directly from the ECU doesn't work...right? This is basically an ODBI car. Old fashion blinking lights

 

Streetwiseguy
Streetwiseguy MegaDork
1/3/20 2:41 p.m.

In reply to vazbmw :

Did you check A6 to see if there is a wire connector in it?

vazbmw
vazbmw HalfDork
1/3/20 3:02 p.m.

In reply to Streetwiseguy :

It does have a connector. I just tried a different ecu, and same issue. So, I am thinking it's an electrical issue, and not an ecu  issue? Thoughts?

Streetwiseguy
Streetwiseguy MegaDork
1/3/20 3:14 p.m.

If A6 has a connector, try it.  You may have an ignition code.

I presume you have this info available?

http://www.matthewsvolvosite.com/read-codes-volvo-850

vazbmw
vazbmw HalfDork
1/3/20 3:44 p.m.

In reply to Streetwiseguy :

Thanks very much. Yes I have that info. A6 only gives me a faint blinking light. No ability to pull codes etc Video of blinking light

Streetwiseguy
Streetwiseguy MegaDork
1/3/20 4:12 p.m.

That's odd.  It also explains why the bulb was out of the dash.smiley

Streetwiseguy
Streetwiseguy MegaDork
1/3/20 4:29 p.m.

The wire in hole A6 goes to pin 7 on the obd connector, pin 22 of the trans module and pin 36 of the ECU.  Maybe unplug the TCM and see whether it will flash codes.

I presume that is a communication line between the modules to back off power when its shifting, but I could be entirely full of E36 M3, too.

vazbmw
vazbmw HalfDork
1/3/20 5:04 p.m.

In reply to Streetwiseguy :

LOL. Yup

vazbmw
vazbmw HalfDork
1/3/20 5:07 p.m.

In reply to Streetwiseguy :

Well, it gets more complicated than that. I did a manual swap a while back, but since having the car (4 years), I have not had a working check engine light. But yes, the TCM is full of codes since it's not hooked to a trans lol. I wish I had known if the check engine light had issues before the swap. At least I could have known if there was some relationship to the current issue

Streetwiseguy
Streetwiseguy MegaDork
1/3/20 5:43 p.m.

Have you tried running it without the tcm?  Need it for some speed signals or something?

vazbmw
vazbmw HalfDork
1/4/20 3:54 a.m.

In reply to Streetwiseguy :

I have not tried yet, I assumed I needed it for speed signals, ABS and Tracs. But, experimentation is calling

Streetwiseguy
Streetwiseguy MegaDork
1/4/20 6:46 a.m.

The only signal might be the output shaft speed.  I'm not sure whether anything needs to see that. It's possible that that is washed through the tcm to ecm, abs, or cluster, but I doubt it.  I think the cluster runs off the abs.  Anything else, the signal would be wrong or redundant anyway.  I think.

vazbmw
vazbmw HalfDork
1/4/20 8:54 a.m.

In reply to Streetwiseguy :

good news so far!!!! I pulled the TCM and the check engine light stays off. I did a test and plugged the TCM back in the light comes on after 5 - 7 seconds. I think this is the solution. Thank you so much!!!!!

I have not driven the car yet, but shall see if things are AOK. 

Our Preferred Partners
GfsekOSili0Yo9M6HZnXejSpEuEAHoNucvcjUgM2gsEHP2fEXBKl6FYP3bvhAzJR