Speedo stopped working & EML is now on 2002 D4D Auto

[Paulmc]

Hi guys, while out today on some rural lanes through some rather muddy puddles I noticed my engine management light came on. I stopped & turned engine off & on, light went out but after a short drive its back on, then noticed my speedo had stopped working. Revs still working as is everything else on the dash clocks.

I thought maybe a speed sensor?

 

[karl2000]

I don't know about the 90 but I've got an idea how this works on the 120, and I assume it's not too different.

It sounds like a speed sensor to me too - you've probably got a P0500 or equivalent code if you read it. It will take the ECU a while to realise it hasnt got a speed signal, so thats why there is a delay before it triggers the engine light and logs the code.

There are two speed sensors on the gearbox / transfer case, if you plug in techstream you should be able to get live data from both of them (I think theyre called NT1 an NT2) and see which one is the problem.

I'd get underneath first and check the wiring and the connections before replacing the sensor(s). The shite from the puddles could have just caused a bad connection.

 

[BobMurphy]

I'm sure you know all this, but just in case . . .

I've seen these nylon gear teeth strip:-

So, which is best . . . A mechanical problem or an electrical one .

For me - mechanical every time .

Bob.

 

[Paulmc]

Ok well I went out today, EML light was off & Speedo was working again untill it started dancing while going down the duel carriage way. Soon as I came off a island it started to lose power as if it was losing drive, then was very erratic.

Managed to pull into a lay by and I’m now waiting on recovery!

 

[karl2000]

:-( Sorry to hear that - get the codes read if you can. If you're getting it taken to a garage, see if you can get the info from them, because we're all curious now.....

 

[Paulmc]

Ok I’ve been under today and noticed that the plug on the speed sensor was loose, it pulled off soon as I pulled it. It was a little dirty so I cleaned it & pushed it back on, now it’s solid on & wont pull off easy at all. That’s tells me it was loose. Hopefully that’s the issue.

Also moved a pair of small plugs on the side of the gearbox & the one pictured had a lot of dirty water pour out of its protective cover.

 

[karl2000]

Great! Fingers crossed... Keep us updated when you test it!

 

[Paulmc]

Yes well I did a 22 mile test drive & so far it’s all good.

 

[karl2000]

P0500 is a speed sensor - there are two of them on the gearbox one by the input and one by the output. If you hook up techstream you can look at the two speed sensors NT1 and NT2 and see which one isnt giving any value to determine which one is gone.

It could be a wiring problem to the speed sensor, or the sensor itself. Give it a physical / visual check first. They're only a 5 minute job to replace.

By speedo meter I assume you mean the instrument cluster?

 

[karl2000]

On the 120 there's two, someone can advise about the 100 but I assume it's the same. Driving the car and looking at the the live data should show where there's a missing signal - either a gearbox speed sensor or (possibly?) a wheel speed sensor.

If live data shows valid speeds but you still get the p500 I'd look at the wire between the ECU and the instrument cluster to make sure the signal is reaching the cluster ok. I think it comes down to troubleshooting via live data and a multimeter/scope on the wires.

Physical check on the wiring first - is the plug ok, good connection no corrosion no obviously broken wires etc. After that it's a multimeter/scope job.

Have you had any other work done on the car recently - anything else happened to it?

 

[karl2000]

By the way - have you checked all the fuses? I assume the garage has, but just having a quick look at the Haynes wiring diagram for the 100 and theres at least 1 fuse (10A) linked to the speed sensor...

 

[karl2000]

10A Gauge 2, if you can find any mention of that in your handbook

 

[karl2000]

My haynes diagram is rubbish, but there will be people on here with proper diagrams who can tell us where the wires run, so you can start checking them.

When the garage had it, do you know if they were seeing a speed on the live data from the ECU?

 

[karl2000]

That's not a separate fault with the cruise control. What's probably happening is, it takes the ECU a while to decide it's not seeing a valid speed signal (there is a process where it has to wait so many seconds). When it decides no speed signal, it gives the p500 and check engine light comes on.

The cruise control checks to see if the engine lught is the on, and if it is, it won't engage.

So once you fix the speed thing, cruise will come back!

Did you check all the fuses?

 

[karl2000]

You need multimeter to test if they're ok - check resistance / continuity across the two test pins on the top of each fuse - you don't even have to take it out.

If you haven't got multimeter, find the ign and/or gauge fuses from the manual, then pull them out and physically inspect them for a breakage between the two terminals - it's usually (but not always) obvious when they've blown

 

[karl2000]

The missing fuses are probably fine, not every car has every option, so they don't need all the fuses - petrol/diesel are different etc.

Also you may have another fuse box inside - not sure about the 100, but the 120 does