Volvo 670 help needed

[kifa]

I have Volvo 670, few days ago a faced a problem my speedometer stopped working(when you go 50mi/h it shows 20 mi/h)
Also sometimes the check engine light flashes and engine starts loosing it's power but when i release and press again gas pedal everything get's to normal.
(The interesting thing is that speedometer stopped working when check engine light first time started to flash)
Does anyone knows solution of such a problem?
Thank you

[allan5oh]

Check ECM wiring on the battery.

[Kranky]

VSS (vehicle speed sensor) at the transmission output shaft is defective, or the connections or wiring between the VSS and the ECM have a fault.

When the ECM does not receive a valid signal from the VSS, the speedometer will read inaccurately or not at all and it will not allow the engine to operate at full power, hence the loss of power when the speedometer is reading incorrectly.

The check engine light is notifying you that the ECM has detected a fault in the system i.e. the problem with the VSS.

[bob h]

Agreed; VSS. Checking the fault code would verify.

[cumminsM11]

You need to check if the problem happens when you try to acelerate or is it all the time. I have the same problem on my volvo, and FLD as well. I called Cummins and got many answers. The one I liked best was when the superviser said check the wire that goes from the VSS to the ECM, it could be bad since it was only happening when I went accelerate. The engine would twist under torque and I would lose my speedo display. As soon as I let off, the speedo would show normal. The Odometer will be out that much as well. As far as loosing power, that is because when the speedo reads below 10k/hr, and the RPM is over the setting for no VSS signal, the electronics go into a preprogrammed setting as if you did not have a working VSS, therefore no power. It took me while to figure out all these things. If you dont want it to lose power, go to Cummins or Freightliner or CAT, and have them reprogram so that the RPM will go to 1800 even if you don't have VSS at any time. Hope this helps.

[Kranky]

You need to check if the problem happens when you try to acelerate or is it all the time. I have the same problem on my volvo, and FLD as well. I called Cummins and got many answers. The one I liked best was when the superviser said check the wire that goes from the VSS to the ECM, it could be bad since it was only happening when I went accelerate. The engine would twist under torque and I would lose my speedo display. As soon as I let off, the speedo would show normal. The Odometer will be out that much as well. As far as loosing power, that is because when the speedo reads below 10k/hr, and the RPM is over the setting for no VSS signal, the electronics go into a preprogrammed setting as if you did not have a working VSS, therefore no power. It took me while to figure out all these things. If you dont want it to lose power, go to Cummins or Freightliner or CAT, and have them reprogram so that the RPM will go to 1800 even if you don't have VSS at any time. Hope this helps.

Why not just find the real problem and fix it the right way?

[allan5oh]

no kidding, quicker and cheaper too.

[enobeenob]

It is the VSS sensor. Replace it is is only $32.00 for the part.

[mikeymike]

Doesn't the vss have to be adjusted/calibrated also?

[cumminsM11]

On the Volvo's there is a second VSS on the top of the shaft. The one that is being used is probably on the side. Unplug it and use the second one to see if that solves your problem. Have you noticed if it acts up ALL the time or only when it is fully warmed up? Mines will only do it after it has been running for about 1/2 to 1 hour. Then it will continue to do it after that.

[enobeenob]

Doesn't the vss have to be adjusted/calibrated also?

No, it does not need to be calibrated. Just R&R and go on down the road.

[kifa]

Thanks guys it was really helpful, i cheked the wires and realized that the battery had not good connection. Now car works fine but the odometer still doesn't work. If i'll change the VSS is it gonna change anything? What else may cause the problem that odometer doesn't work?

Have you noticed if it acts up ALL the time or only when it is fully warmed up? Mines will only do it after it has been running for about 1/2 to 1 hour. Then it will continue to do it after that.

It's sometimes shows the right speed but most of the times it's just dead or stuck on any random number. It's doesn't metter if you just started the car or driving a long time it's always the same.

[cumminsM11]

I just got my truck back from the shop after the CVI and the yoke nut was tightened at the same time. The pick up for the speedsensor is on that output shaft of the transmission. You will need to go under the truck and see if there is any play in the output shaft of the transmission. Push it up. if you can move it up, 90% chance that is your problem with the speedo. When you accelerate the output shaft moves and so does the pick up for the VSS, causing an erratic reading. That is why when you took you foot off the throttle, it went back to normal. I had the same thing happening to my Volvo, and my FLD. Tighting the yoke nut is about 2 hour job, and your truck will also run a lot smoother. Now I have no vibrations at any speeds at all. MY SPEED IS SHOWING ACCURATE AFTER ABOUT 4 MONTHS OF THE NEEDLE JUMPING UP AND DOWN. My speed would also show OK after I let off on the throttle, and drop after I stepped on it. As the play gets worse on the output shaft so will the frequency of your speed not reading right. Also when you climb hill with a load and start shifting down, with every down shift, the needle will drop more and more. I got different answers from a few shops. What they said was not making much sense so I just left it. i am glad that the mech. tightened up the yoke nut and that was the problem all along. Anyways Good Luck with the problem. (Just curious, is it a car or the Volvo you were inquiring about, you mentioned the CAR is running better now with the battery connection all fixed up.)

[Kranky]

Cummins M11 wrote:

When you accelerate the output shaft moves and so does the pick up for the VSS, causing an erratic reading

If the yoke is loose that will allow the trans. output shaft to move axially, but the VSS is screwed into the bearing retainer/seal housing on the transmission, and locked in place with a jam nut. I can assure you that "the pickup for the VSS" ain't gonna move.

If it does, you've got bigger issues going on.

[kifa]

My speed would also show OK after I let off on the throttle, and drop after I stepped on it. As the play gets worse on the output shaft so will the frequency of your speed not reading right. Also when you climb hill with a load and start shifting down, with every down shift, the needle will drop more and more. I got different answers from a few shops. What they said was not making much sense so I just left it. i am glad that the mech. tightened up the yoke nut and that was the problem all along. Anyways Good Luck with the problem.

In my case the engine works fine. I changed the VSS and still i have problems, odometer works when i start to drive but when i drive few miles it just stops working at all. Also on the car the backlights doesn't work(on the trailer works fine) Also when i drive on a bad road on few seconds engine break and cruise control stops working and computer shows a message "Check line control module".
What may cause this problems? Is this one thing that causes all this problems or there is a lot of small problems i have to find and fix???

[Kranky]

From my earlier post:

VSS (vehicle speed sensor) at the transmission output shaft is defective, or the connections or wiring between the VSS and the ECM have a fault.

It sounds like you have other wiring issues as well, causing your light problems.

A wiring harness is probably chafed somewhere and the vibration and bouncing while driving are causing an intermittent connection or short circuit.

Time for some detective work..

[cumminsM11]

I am just saying that I had the same problem, speed shows low when accelerating and OK when you are not touching the throttle. I never suspected the loose output shaft, but that was what teh problem was. So you can all say what you want. If it was the VSS, it would be doing it all the time. Anyways I am just speaking from what I have experienced. You can change anything you want on the truck. It will not fix your problem until you tighten the yokenut. 2-3 hour job, or put some washers behind the shaft like we did. Anyways what do i know. have a nice day.

[Rat]

I have been in contact with a Volvo repair shop and they also mentioned a loose Yolk causing this problem. But The one I drive has the Meritor 10 speed. Check the VSS adjustment first along with checking for looseness of the output yolk. Turn the VSS in untill it bottoms out then turn it out 1/8 to 1/4 turn. Also drop the drive shaft and tighten the yolk nut and see what happens.