Renault Twingo Battery light on

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paullap
OneWave
OneWave
Posts: 13
Joined: Sat Oct 27, 2018 2:07 pm

Renault Twingo Battery light on

Post by paullap »

Hi I am having trouble sorting out a Renault Twingo 08 plate Battery light on problem. It comes on after about 30 seconds.

The Alternator has only one control wire and the main wire that goes to the starter.
Fault code
DF137 UCH Alternator connection.

I have scoped the LIN wire and get a square waveform, But very low voltage 0.3 to 0.65 MV. Not sure if that is what it is supposed to be.
My question is , If I have a bad connection on one end of the LIN wire, would I see a wave form?. I know the message goes both ways on this wire, so if one end has a bad connection am I seeing a wave form generated by the Alternator.

I have been told that if I disconnect the LIN wire from the alternator it should charge. I have also read that it needs to excited by the LIn wire to start charging.
Any help would me much apreciated

Paul Armature Pico mechanic.

Technician
TwoWaves
TwoWaves
Posts: 706
Joined: Thu Apr 24, 2014 8:32 pm

Re: Renault Twingo Battery light on

Post by Technician »

Hello,

Your LIN voltage seems low, have a read;

https://www.picoauto.com/library/automotive-guided-tests/lin-bus/

Iver
TwoWaves
TwoWaves
Posts: 182
Joined: Mon May 27, 2019 2:55 pm

Re: Renault Twingo Battery light on

Post by Iver »

I have scoped the LIN wire and get a square waveform, But very low voltage 0.3 to 0.65 MV. Not sure if that is what it is supposed to be.
Hi Paul
That is your Issue for sure. I dont have a diagram to hand but i would guess that wire goes from Alternator to to the UCH (or PCM ???) You can set me straight on that.

You either have a Bad Controller, Bad Alternator, Bad Wire or Connector Issues.

First Unplug Both ends of that wire looking for proper contact, Pins Clean and Tight, Corrosion, Moisture etc.There may be a connector or two in the loom that the wire passes through, unless they are easy to find and access then dont worry too much for now, we can narrow it down for now from the 2 ends of the wire.

I would unplug from Alternator then scope the disconnected wire. That should have a Good Linbus Signal on it, Good Square Wave with near battery voltage. Your Linbus Signal will improve massively IF the fault is within the alternator. At the same time use Channel B with a break out lead on the Alternator Connection.

You should see a Good Linbus Signal on both Channels on a GOOD Car. If the Alternator is the culprit then you know where you are.

If the Alternator is good then it is the Wire or the Controller. Connect the Wire back on to the alternator

Next, Identify the wire at the controller and either open up the connector and remove that Single Wire.

It has to be Just that ONE wire you pull out or you can lose the opportunity of spotting cross contamination in the loom. If removing the wire is tricky then Cut that wire close to the plug but where you can easily repair it again.

Now scope what is coming out of the UCH and what is on the wire. Again with a GOOD Car you should have a Good Signal on both. Now You will know if it is the Controller or the Wire.

You could very quickly now Bridge a new wire direct from UCH to Alternator (old wire unplugged or cut at both Ends) to eliminate the wire conclusively.

Let us know how you get on and would be good to see Before & After Captures.

Iver
TwoWaves
TwoWaves
Posts: 182
Joined: Mon May 27, 2019 2:55 pm

Re: Renault Twingo Battery light on

Post by Iver »

  • 1
I have been told that if I disconnect the LIN wire from the alternator it should charge.
  • 2
I have also read that it needs to excited by the LIn wire to start charging
Every Smart Charge I have looked at behaves as "1" The alternator just goes on charging like the Old Skool Alternators without software control. Again that will depend on the particular Fault in the Alternator so that really is not a 100& definitive test. The "No Scope No Hope" brigade will rely on those old wives tales !
Armed with a scope, us the "#Test not Guess" Brigade can actually evaluate what is going on

"2" Could be the case in some vehicles. I have never seen that myself. However if that is written into the DNA of the car then that is what will happen.

Another option to my first post is use a (Micro) Amp Clamp to determine Uni or Bi Directional activity however with those tiny voltages (i'm guessing current will be tiny too) it may not be so conclusive.

When that Linbus is all good then it can. I have done it on a BMW Glow Plug Module Lin wire before and after Replacement and it was clear to see one way traffic before and two way after. I could see which node was transmitting what.

That was a faulty Module. I could see good clean linbus signals at the right Voltages but a DTC would not go away

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