ECU power voltages. RED light solid issues. lots of checks already carried out!

[lewisredfern001]

Gents
my missus 172 cup wont start.

ive searched/read various posts over the last 24hours on here with some great help but to none avail, and am running out of options.

symptoms are:
key in ignition to stage 2 and red light stays constant - i am lead to believe this could be the purple/white twited wires having a break.

fixes tried:
continuity checked from UCH plug pin 19 and 20 to the relevant pins on ECU plug, 27 and 57. Continuity is fine showing no breakages.
next up i have run 2 new lengths of wire form the uch to the ecu on the above pins, incase there is maybe a voltage drop on original wires. i am still not getting the light to go out, hence it not starting.

next steps:
checking voltages and more continuity tests? however i am not sure where i need to be starting. after the above have been checked?

i am after some expert help and am willing to pay for it, wether it be over the phone or in person, i have 3 days off and i am going to fix it!!!

thank in advance
lewis

 

[pendulumx]

Following with interest, good luck

 

[MicKPM]

I'd love to help but over the phone this will be nigh on impossible to track or advise on i'm afraid... really would need to see.

Mick

 

[lewisredfern001]

From experience mick what else could cause this? Or would you still think wiring issues? ecu power Problem? UCH? I'm really wanting the Ecu pin outs diagram,so I can work out where I should have 12v, or where I should have signal voltages. I'm no auto spark but an electrical/mechanical engineer, so fairly confident and I am going to try and solve this myself over the next week before I think about taking it anywhere.

If anyone has any diagrams which will help they will be greatly accepted!!

 

[MicKPM]

Personally, and without seeing the car, i think it'll be either a power or an earth issue to the ECM yes. I don't have my wiring diagrams to hand i'm afraid but the main +12v feed is known from breaking in the 90deg bend and gives the same results as what you are seeing.

Mick

 

[lewisredfern001]

I'm going to go through the same as what I done today again. I have stripped the loom back to where it splits of at the 90 degree bend but I think I still need to go further back, but its a pain with the coolant pipes in the way. I may strip them out in the morning

 

[TrackdayAl]

PM me your email, also vehicle year etc I probably have the diagram.

 

[MicKPM]

wait till you get a diagram then check for power at the relevant pins... just run a new, dedicated power line from the white R65 connector in the bay fusebox to the ECM. Saves time and faffing around.

Mick

 

[lewisredfern001]

the white wire being, Pin 27 of the ECU plug to Pin 20 of the UCH. if so i have already ran a dedicated wire from the uch pin out to the ecu. i piggy backed the wires?

 

[Dave Hester]

Just had this EXACT problem on my 172 cup too and im sure you have read my posts/ threads

Every expert i spoke too all said that 99% of the time, when u have a constant red immo light, its a break in the wiring somwhere.

You need to strip all the sleeving off the wiring going to the ecu and see what u can find.

The break i found was a thin white wire that twisted round a thin purple wire. ( there is also a thicker twisted white and purple wire)

The break was in the loom - going from the ecu follow the wiring down to where it branches off towards the rad.

My break was 4 inches from there

 

[lewisredfern001]

Ye I've read your problems, I'm still convinced its a break in a wire. However I have run a new cable from the uch direct to the Ecu with still no luck? Gonna try again 2mro in between helpin the Mother in-law move house and going to see Santa with my son!

 

[Dave Hester]

Theres 100% nothing wrong with your ecu, uch, key, code, or decoder ring

Is 99% a wiring issue

Or the other 1% a earth problem

 

[Wooky12345]

Any luck fixing this Lewisredfern?

 

[lewisredfern001]

update - but in a word NO its not fixed. i have only had an hour or so to play around since i last updated.

testing completed

Pins tested:

power 12v+ - Pins 29 &30 All fine, i did try and measure voltage drop when cranking. and noticed it drop to around 8v? on both pins

Fuses (engine bay) - 1,3 and 5 All fine
Earths - Pins 3,28,33 and 67 All fine
pins 61 & 62 continuity tested (the thicker white and purple twisted pair, i traced back as far as possible which was round the front of the engine by fuel rail)
continuity from UCH to ECU between Pins 27 (ecu) - Pin 20 (uch) all ok
57 (ecu) - Pin 19 (uch) all ok
Just to be sure i ran new wires from uch direct to ecu to ensure there was no breaks

I have also tried a number of 'key resets', unplugging and re-connecting decoder ring. moving decoder ring into diff positions incase it wasn't picking the key up. All this resulted in was a constant fast flashing red light.

 

[lewisredfern001]

Earths measured and are 0.005 and 0.008 ohms.

 

[Dave Hester]

Your looking in the wrong place, the break in a wire will be from the white multiplug to the ecu.

Take out the airbox, battery and ecu case, then disconnect the plug from the ecu and pull all the black plastic sheath off the wiring and check every wire, taking special attention to the white and purple twisted wires.

The break will be either on the 90 degree bend before the ecu or further down the wiring after it branches out towards the car

 

[lewisredfern001]

That's exactly what I've done m8, all wiring is stripped back. I've tested from the multiplug to the Ecu. From the multiplug back to the uch. And put a wire from uch to Ecu to basically bypass the twisted white an purple pair.

The only reason for testing the thicker white and purple which run around the front of the bay is because they have been mentioned in posts I've read.

 

[Dave Hester]

So its still a solid red??

 

[lewisredfern001]

Ye solid red, but all the signs of a wire break, I've cleaned up all the relay pins aswell as they where a little grubby

 

[Dave Hester]

Check to loom again, some wires are that thin and tiny that the break is hard to spot.

Eventually i found a thin white wire that looked a bit squished, looked at it more closely and it had green powder on it (this is from corrosion of the copper wire inside) cleaned it up and sure enough there was the break

Also check the wires going to the lamba havent melted together with the heat from the manifold.

 

[lewisredfern001]

I've got all day 2mro to strip some
More loom back. After that I will admit defeat.

 

[lewisredfern001]

everything has been checked and re-checked, as mentioned above. Is there any pins i haven't mentioned which should have 12v on them. i don't want to pay an auto electrician unless he has renault experience. Plus i think ive checked all that he would check. not having the relevant data/diagnostics (CLIP) is where i am now stumped.

i was thinking i could pay renault to put it on there clip to just see if they can point me in a direction. unfortunately i am just one of those people who would rather try and fix it themselves!

 

[Dave Hester]

Have you pulled the white multiplug apart and checked for corrosion??

Swap the black relays around?

Checked the earth strap on the gearbox is tight and not broken??

Clip machine will relieve you of £70 and tell u that u have a wiring fault

 

[lewisredfern001]

just done some more testing and found wire 66 which im led to believe is + after ignition, which should be 12v. well it 4V. i havent put a 12v supply to it as i just want confirmation that it is 12v!!

earth strap on the box is fine

 

[lewisredfern001]

even with 12v running directly to pin 66, it hasnt changed anything

 

[lewisredfern001]

I'm looking for someone in the south east to fix this for me now if anyone knows someone who can help?

 

[MicKPM]

I'd offer mate, you know i would but you're just too far to be viable.

Mick

 

[TrackdayAl]

Where abouts in South east?

 

[lewisredfern001]

Folkestone in Kent. I do hav the ability to get it moved on a truck but am trying to keep costs down as its Christmas!!

 

[lewisredfern001]

Mick,

You've been great taking time out and your help and knowledge has been great but yes unfortunately I don't think it's going to be cost effective.

 

[TrackdayAl]

http://www.kentcarcraft.co.uk/

Owen the boss is ex Renault, Dan his diag guy is very good and they have clip.

 

[lewisredfern001]

Goin into see a man who has seen/rectified this fault before who is 2 miles from my house. Although its main dealer I plan to have a good old chat with him before they start trying to charge me big bucks. Hopefully have an update thursday afternoon

 

[Dave Hester]

Still think its a broken wire in the loom

Good luck mate, i know what an utter pain, jobs like this are

 

[lewisredfern001]

I'm under the same impression but I've checked the wires suggested and they seem fine? Maybe a voltage drop I can't find? Or another wire I've not checked

 

[Sean6545]

Have you checked the earth on the gearbox near the loom you have been playing with? 13mm bolt iirc.

 

[lewisredfern001]

Ye earths all Seem good

 

[Fred@BTM]

i still bet its something so stupid you've just missed it

i had one where the lambda wire melted against the exhaust - same problem, took me a while to figure that one out!

 

[Mike@Rentech]

Broken multiplex wire in loom near ecu, pull loom apart in engine bay look for white grey twisted wires one will be broken.

 

[lewisredfern001]

Lambda wires are ok. Also the loom is stripped right back. Nothing obvious broken or any signs. I think it's something stupid that I've missed aswell. Working outside in the cold and wet leaning into the engine bay after night shifts or before late shifts hasnt been the most Motivating.
Only thing I can think of is low power to Ecu that I haven't been able to detect with my meter

 

[MicKPM]

The offer is still there mate... if you've not fixed it with fire!