306 Hdi - Speedometer not working - Electrical gremlins?

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Pugfan306HDI

Member
Tadpole
Joined
Aug 21, 2017
Messages
42
Location
Melbourne
Hi Aussie Froggers,

Speedometer on the cluster stopped working and have had the sensor replaced which has had no effect. My Mechanic has suggested this could be an electrical problem - has anyone has this issue and know how to rectify? I feel that there is a slight loss of engine power too when speedo stops working

Oddly enough, the turbo just started working after an 18 month rest. Could this be related?

I have booked the car in to an auto electrician next week and would be good to hear from the community what to test/look out for.

Thanks!
 
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Try wriggling all the fuses around. On my daughter's late model XSi, I had to do this 3 or 4 times and it fixed it. Actually I pulled all the fuses out one at a time and put them back in again.

Good Luck it can't cost too much to try.
 
BIGRR said:
Try wriggling all the fuses around. On my daughter's late model XSi, I had to do this 3 or 4 times and it fixed it. Actually I pulled all the fuses out one at a time and put them back in again.

Good Luck it can't cost too much to try.
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Thanks - will give it a try. Saw a vid on youtube suggesting disconnecting power for 5 minutes may also help
 
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Pugfan306HDI said:
I feel that there is a slight loss of engine power too when speedo stops working
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That's because the computer uses the speed signal to adjust the throttle sensitivity. If it doesn't see a speed signal, it defaults back to its least sensitive setting, requiring more throttle input for the same engine power.
Pugfan306HDI said:
Oddly enough, the turbo just started working after an 18 month rest. Could this be related?
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If this is a HDi, excessive turbo lag and lose of power can be caused by the MAF sensor failing.
I have heard that unplugging it, to see if power output changes, is a good diagnostic step. (although I have never tried this myself).
 
Thanks @gromzx @BIGRR.
An update - after removing and replacing all fuses I took the car for a drive. Speedo still not working. After about 15 minutes drive there was a furious clicking sound in the vicinity of the fuse box which I suspect was a relay going haywire. Pulled over and switched engine off to investigate but could not see anything obvious. I then Restarted the car and now speedo is working. After a few more trips speedo is now working consistently.

@gromzx would a failing MAF sensor stop the turbo from working?
 
Pugfan306HDI said:
@gromzx would a failing MAF sensor stop the turbo from working?
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It's not that the turbo isn't working. The computer does its max fuel calculation from the air flow it sees at the MAF sensor, rather than a boost pressure sensor. So if the air flow value the MAF sensor is sending to the ECU is too low, you will be stuck at the lowest max fuel value, limiting power output.
Hopefully my explanation makes sense.
This problem can be intermittent.
Do you find that you sometimes get power and sometimes don't, or do you find that it feels like the turbo takes a long time to do anything?
 
gromzx said:
It's not that the turbo isn't working. The computer does its max fuel calculation from the air flow it sees at the MAF sensor, rather than a boost pressure sensor. So if the air flow value the MAF sensor is sending to the ECU is too low, you will be stuck at the lowest max fuel value, limiting power output.
Hopefully my explanation makes sense.
This problem can be intermittent.
Do you find that you sometimes get power and sometimes don't, or do you find that it feels like the turbo takes a long time to do anything?
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Yes, I would say turbo is intermittent. So I guess I could try unplugging it and seeing if there is any difference. To replace is the best done by a mechanic or an auto electrician?
 
It's easy to replace. 2 screws, 1 plug and a hose clamp. Don't forget to take the o-ring off the old one and put it on the new one before refitting.
I'd upload a picture, so you know what to look for, but I don't own a 306 anymore.
It's attached to the top of the air box.

Found a pic.
 

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Just as an update for anyone later on who has the same issue, removed MAF and was dirty so cleaned and now engine is running as new. Speedo still not resolved but am hoping to resolve next week
 
Frenchiemech34 said:
Any luck with the Speedo fault
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No yet. This far have had it a an auto elec who has swapped out VSS x 2, and had instrument cluster inspected. Auto electrician had car for over 2 months and I had to wrestle it back from him. A bizarre experience and above his capabilities. Have it booked into a recommended auto elec and am asking him to do normal continuity and sesnsor checks, check grounds and run new wires if nothing is obvious.
 
Just to close this thread thread there was no issue with the instrument cluster at all. First auto electrician I engaged had my car for 9 weeks and could not fix - instead they did more harm than good. I had to retrieve my car form them as they were hopeless.

Took car to Rob's auto elec in Brunswick and he was able to fix issues - can't recommend going to him highly enough. He had to undo some of the bodged work of the previous auto electrician so its hard for me to determine what the original fault was. Main issue corrected in a nutshell wasL
1. Internal speedo gear was missing - this is on the output shaft of the gearbox. He sourced a replacement from Peugoet
2. Speedo sensor wiring- New wiring run from sensor to instrument cluster but not to ECU. ECU needs to know speed as well so signal was rejoined to ECU
3. MAF sensor plug lock mechanism missing - signal was dropping out due to loose connection. New lock added to plug.

I suspect the original issues was caused by a broken wire from VSS to ECU and the loose MAF plug. Super happy to have this issue resolved and if you have any issues and based in Melbourne would recommend reaching out to Rob's auto elecs
 
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