850 Transmission not shifting up

dramsfield · Post by **dramsfield** » 16 Mar 2009, 10:08

I have a 1995 Volvo 850 glt, with automatic transmission. The transmission has gone into safe or limp mode with the shift up arrow flashing. I have changed the gear position sensor but there was no difference. I also changed the TCM with a known working one. No change. When I insert the test lead into position no. 1 of the computer, the red light lights up and will no go out. So at this point there is no way of getting the diagnostics. The problem has been intermittent in the past but now is consistent. Will not shift into low starts out as it is in econo mode. I have also changed the econo sport mode switch. I think the self diagnostics is grounded somewhere. Having worked with a volvo mechanic on this he now thinks it is the solenoids in the transmission and that the transmission itself will have to be replaced. I am convinced that it is electrical due to the flashing and intermittent nature of the problem, and the lack of availability of the self diagnostics.
Thoughts anyone. What is causing the light of the self diagnostics to stay on? How do you test the solenoids in the transmission without removing it. Could this be connected to the ABS somehow which is also not working.

Post by **MadeInJapan** » 16 Mar 2009, 11:06

Welcome to MVS.
Have you read the diagnostic trouble codes?
This sure sounds like a PNP switch to me.

Post by **Ozark Lee** » 16 Mar 2009, 11:52

Does the diagnostic test port behave the same way with the other TCM? It is easy test the solenoids but the code port needs to be working to do it.

...Lee

dramsfield · Post by **dramsfield** » 16 Mar 2009, 13:04

Thanks to the prompt reply. At first I thought it was the Gear Position Switch/Sensor or I think it is also called the PNP switch? I installed a new one but prior to that did take the old one apart and found no pitting etc. Looked clean but I used very fine wet and dry and then some dielectric grease. No change so I put the new one in. We alligned it paralled to the casing mark as recommended by volvo. I can read the diagnostic codes for both the Engine Control Module and the ABS control Module, but not the Transmission Control module. So readings out of both #3 and #2 but a constant read light for #1 and no ability to clear.

95autoturbo · Post by **95autoturbo** » 16 Mar 2009, 15:14

Found this...

"Reset the box by making sure you have selcted economy and not sport, that the box is in summer and not winter setting. Switch off the engine. then swithch on the ignition without starting the engine. Move the gerat selector to drive, back to park, then agin, sometimes yoou need to do this tree or four times. the flashing arrow with switch off. switch off the ignition. Now start the car as usual, your box should be back to normal and the flashing arrow should be off. If not, try again. It has worked on all of my cars, four so far.. Jon"

Just tried it on mine and it worked.

dramsfield · Post by **dramsfield** » 17 Mar 2009, 09:48

Thanks for the information on resetting. I tried the econo mode and summer position, turning engine off and moving the shift from park to drive. Shifted back and forth at least a half dozen times. No change as the light is still flashing. No ability to read codes. I think this would work with a defective gear position sensor, which leads me to think it is something else. I tested the continuity of the lead from socket #1 to the transmission control module, also thinking that there could a short to ground there, but there isn't. The test lights go on when the circuit is made to ground.

If it is a transmission solenoid I am told that they cannot be purchased and that the whole transmission has to be replaced. How easy is it to access the transmission solenoids to test them? And if one is defective, can they be rebuilt? Asian makes transmissions for more than just Volvo. Are transmission solenoids interchangeable from one model to another. Where do I look to get the information on what transmission solenoids are used in this transmission?

Post by **Ozark Lee** » 17 Mar 2009, 10:26

If it is a transmission solenoid I am told that they cannot be purchased and that the whole transmission has to be replaced. How easy is it to access the transmission solenoids to test them? And if one is defective, can they be rebuilt? Asian makes transmissions for more than just Volvo. Are transmission solenoids interchangeable from one model to another. Where do I look to get the information on what transmission solenoids are used in this transmission?

FCP Groton sells the solenoids.

http://www.fcpgroton.com/category-exec/ ... by_year/45

The hardest part about changing them is the getting the cover pan off. I think you still need to figure out why you can't pull the codes before you start throwing parts at it. If you can get the test port to work you can put the TCU into test mode and exercise the solenoids.

...Lee

dramsfield · Post by **dramsfield** » 17 Mar 2009, 11:03

Lee, thanks. I agree. If I can get it out of limp mode then I suspect that the test port will function. Will keep trying.

binglax09 · Post by **binglax09** » 17 Mar 2009, 18:07

How does the tranny fluid look?
Have you tried unplugging the ground for a while to clear the code that way?

Also, it's most likely not the solenoid that is the issue, it sounds more along the lines of a bad ground or some type of wiring issue. I have a complete set of solenoids if you need them.

This does not sound like an internal issue in my opinion..

drsugg · Post by **drsugg** » 17 Mar 2009, 19:04

I would suggest finding a shop with a factory scan tool for Volvo. These will plug into the test box and may answer a lot of questions. I've always been able to buy the shift solenoids from Volvo, no problem. I haven't tried in a year or two so who knows about now. Replacing the solenoids on the car is possible, just unbolt the motor mounts and start jacking the motor. It's been a while, but I think you need to pull the left axle and possibly a bit more. I have encountered wire harness issues with 850 transmission and without the Volvo scanner, I might have not been able to diagnose it. Get the wire diagrams and start checking at the TCM plug, could be something obvious with power/ground supplies.