P0118 non start issues

Andy.MacFadyen wrote: You could try work around, use a DC/DC 12v to 5v step down Buck Converter voltage supply to provide the 5v reference.
A couple of pounds spent on ebay might save replacing the computer.

I like this idea.

Also, the voltage readings at your APP are different from what I was expecting. :lol: Wondering if there's some kind of idle validation switch at work, instead of two potentiometers. Does the wiring diagram show any kind of internals on the APP?

No I can't see any internals.

There does appear to be two 5V references though, no?

Is it the higher voltages 10.7 & 9.2 that you were not expecting ?

Unsure how I would wire in a 5v regulator, does it not have to be part of a voltage divider circuit in that it would need to be going through a resistor before it gets to the thermistor ?!

thx

mckenzie wrote: There does appear to be two 5V references though, no?

Is it the higher voltages 10.7 & 9.2 that you were not expecting ?

I wondered, but the 4.7V reading is a bit low. Not like the 3.3V you saw on the ECT, but still somewhat low. There's definitely one 5V and two grounds. The others, yeah, not sure what to make of those. :lol: I guess it makes sense that Renault would do things significantly differently than the domestic and asian makes I'm used to. :blush:

Peugeot not Renault Thanks for all the input, whether another sensor or wiring could pull the voltage down is still something thats not entirely clear & with the diagram you posted it would seem this is actually possible, but like you say I should be seeing more codes popping up if it was the case.

I think I need to think this through a bit more, pretty difficult though with wiring diagrams that don't show proper voltages etc! Im wondering now just how many 5V ref circuits there actually are. I need to try & identify them somehow & test.

Thanks guys

Hi, I sent the ECU away for testing, it has come back with a full bill of health! See attached.

Stumped !

Sounds like you specifically mentioned your ECT concern in the repair order, right?

Just for giggles, have you tried reinstalling the ECU and seeing if it's still doing the 3.3V thing?

Thanks Tyler.

Yeah I did mention the P0118 code & asked them to check all 5v references.

I just put it back in the car & it started straight away !!!?? Took it for a spin & everything is running well. However now my front left dip doesn't work & 3 of the 4 fog lights don't work!

Obviously it's pretty good news but am baffled by this, any ideas what has happened here ?

cheers

I'm... Stunned. :blink: Half thrilled that it runs, half pissed off that I missed the actual problem. :lol:

The only thing I can think of is some kind of ECU pin issue, either resistive or shorted to another pin. But, you didn't see any corrosion, and you very likely cycled the ECU connector several times during testing. Plus, why would a trip to the ECU doctor fix that?

I've seen cases where power cycling the ECU for a long period of time fixed weird glitches, BUT this was a hard electrical fault. Again, you had the ECU disconnected, so we should have ruled that out.

However now my front left dip doesn't work & 3 of the 4 fog lights don't work!

Googled helped me out here. :blush: That's a low beam in 'Murican-ese, right? Are the fog lights and headlights controlled by this ECU?

Yeah this is all really strange, going to be scratching my head over this for a while! Ha, yeah dip is low beam in your language I changed the bulb & all is well now. Everything is running very smoothly, thanks again for taking the time with this.

No problem! I'd love to hear back if you have any more problems with this ECU, though I've got my fingers crossed that everything keeps working for you.

Ha, yeah dip is low beam in your language I changed the bulb & all is well now.

:lol: Another reason I love having international members around here - I learn new car slang terms all the time!

If you get the opportunity, I'd also be interested to know if the ECT signal wire now shows 5V when disconnected like it's supposed to. Mostly just wondering if the ECT thing was a red herring, and there was another issue at work.

mckenzie wrote: Thanks. Just to make sure I really understand the voltage divider circuit, is it the case that in order for it to function properly it needs its own dedicated 5v & this 5v cannot be shared with any other sensors. The ECT then will have its own dedicated 5v regulator? This is probably what you were pointing out with the video but I want to be absolutely sure I get it!

Is the engine turning over and not starting ? Or not even cranking ?


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I didn't read all of the replies but I have heard some of the Euro cars using a lower than 5v ref to some of their sensors.
And 3v is the number that came to mind.
I recently worked on an Audi that used a 3.3v bias to all of the outputs on the computer system as well.
For some reason, this 3.3 volt unplugged signal you are seeing on the ECT may be normal.

ScannerDanner wrote: I didn't read all of the replies but I have heard some of the Euro cars using a lower than 5v ref to some of their sensors.
And 3v is the number that came to mind.
I recently worked on an Audi that used a 3.3v bias to all of the outputs on the computer system as well.
For some reason, this 3.3 volt unplugged signal you are seeing on the ECT may be normal.

THIS is what I was wondering about after the ECU got sent back! :woohoo: It's also why I was interested to see if that ECT signal wire still reads the same as before.

If it does, then it suggests that there was another problem at work, and the ECT thing was a big ol' wild goose chase.

Iceman1967 wrote: Is the engine turning over and not starting ? Or not even cranking ?

Initially it was a crank no start, but she's running just fine now.