3.0 went into limp mode - throttle or DSC ?

[mrscalex]

My 3.0 went into limp mode last night. Well it was beyond limp mode really. It just wanted to surge continuously between about 500 and 1000 rpm.

As luck would have it I had INPA on a laptop in the boot. We took a note of the errors. Cleared them down and off we went again. Although I suspect it wasn't clearing the errors but the problem coincidentally reset itself.

These are the relevant errors:

Engine

160 Lambda Post Cat Bank 2 (MS41) or Throttle Valve Stuck
161 Throttle Valve - Stuck
135 Throttle Valve Re-Adaptation Required (think this just reflects it's gone into limp mode)
115 Reference Voltage - Voltage Regulator 1 or Throttle Pedal Adaptation (MS43)

DSC

5E21 Pressure sensor 2
5E19 CAN DME/DDE Torque Reduction Not Possible

And of course the dash was lit up like a Christmas tree with EML & ABS lights.

Initially I was drawn to the DSC pressure sensor (on the master cylinder) and/or a faulty DSC module. I thought these might be sending spurious instructions to the throttle.

But the more I think about it, the more I think it's a throttle issue and the DSC is just saying it's lost it's ability to control the throttle.

All that side of the engine has been out recently and cleaned during routine maintenance. And the car has performed faultlessly for several hundred miles since. So I don't think it will be a simple clean the throttle body.

I've got no issues with changing out the throttle body, both pressure sensors and the DSC module if required. But I don't like not knowing what's going on and worst still it may not fix the problem. And this is quite a scary thing to happen again if you are in the wrong place. Fortunately we were on a local road near home when it was very quiet.

Any ideas for a logical approach to establish the true root cause? Might be in @Murray Wall 's knowledge area?

 

[Mario]

Hello - I have had multiple cars with that same DSC module and diagnosed various of those faults to pressure sensors, rotational sensors, ABS wheel speed sensors etc - I have been driving those cars with the faults until I fixed them with absolutely no problem with driveability despite the amber lights being on the dash - so my advice is start looking at the throttle part first.

 

[mrscalex]

Hello - I have had multiple cars with that same DSC module and diagnosed various of those faults to pressure sensors, rotational sensors, ABS wheel speed sensors etc - I have been driving those cars with the faults until I fixed them with absolutely no problem with driveability despite the amber lights being on the dash - so my advice is start looking at the throttle part first.

That's interesting thank you. I'm certainly inclined to agree with that line of thinking. I'd just like to prove positively it is the throttle body that needs swapping out - not sure it would be anything else in that area unless it's a loom/connector issue.

 

[NZ00Z3]

The 3.0 L Z3 has the MS43 DME. The Bentley manual on page OBD-34 lists all the DME codes you have logged. They are all Throttle valve adaption or throttle valve position control errors.

I agree with Mario, start at the throttle body. The twist electrical connection on the throttle body can be a pain, so check it well.

 

[mrscalex]

We all seem to be thinking the same thing. So I have a replacement throttle body on order. I would imagine the sensor integrated into the unit has gone faulty.

Thank you both for valued input.

This was my first breakdown in many thousands of miles with Z3s over 5 different cars so no complaints bearing in mind these things are 20 years old. Mind you the car in question had just been treated to a refurb'd set of split rims so I was a little dissapointed in the atitude...

Awaiting new centre caps.

 

[Mario]

Where did you get the refurb done? PM me some details I need to get some exact same ones done

 

[mrscalex]

Where did you get the refurb done? PM me some details I need to get some exact same ones done

Platinum Alloys in Swindon. They did the lot including splitting them without breaking any bolts.

I'm going to be hyper-harsh and only give them 9/10. They did catch the odd small particle of dust and the rears they pay a bit less attention to. But for £500 I'm happy it was good value for money. You can pay a lot less and risk have someone stuff them up. You can pay more with little additional benefit.

 

[mrscalex]

And of course you can split them yourself and get them blasted by a local general purpose blasters. Then spray them up yourself. But then you have to get the tyres removed and put back. Risk breaking bolts and needing to get them extracted. And find the perfect compromise between building paint up over corrosion and not loading so much the inners won't go back on. I'll have a go at most things but I think this is too specialised to get a good job done with any degree of ease.

 

[abh29]

We all seem to be thinking the same thing. So I have a replacement throttle body on order. I would imagine the sensor integrated into the unit has gone faulty.

Thank you both for valued input.

This was my first breakdown in many thousands of miles with Z3s over 5 different cars so no complaints bearing in mind these things are 20 years old. Mind you the car in question had just been treated to a refurb'd set of split rims so I was a little dissapointed in the atitude...

View attachment 150689 View attachment 150691

Awaiting new centre caps.

Are you going to the Non Rotating centres ?

 

[mrscalex]

Are you going to the Non Rotating centres ?

Nope I’m strictly how it left the factory wherever possible.