[madbadandold]

Got the car back and removed the bumper for access to rad coolant fan equipment. The fan does not run on test in the low speed selection. Today I disconnected the control wires plug and identified the low speed relay control relay connections to connections 85 and 86 on the relay. The car was not switched on but its battery was connected. I slaved in the two control wires to a separate battery and lo and behold the fan ran at low speed. So the problem lies in the control wires from the disconnect plug to, I assume, the ecu. With car power on I get battery voltage on one of the cables which feeds 86 on the relay. So the other cable is the return from 85. I checked the continuity of this as and was expecting it to be the earth but there was no continuity. Now I am assuming that this is the control circuit which means it is looking for an earth when the coolant temp reaches the low speed fan trigger point through the ecu. But during the fan tests the low speed fan does not test. I assume the ecu overrides the sensor and supplies the required signals to allow the fans to test. So from that I reckon the sensor is OK as it was replaced when I fitted the new thermostat module. So I assume the fault is either a wiring fault on that cable or the ecu. Any thoughts?

 

[madbadandold]

Come on guys. No electricians among you?
Anyway I reckon I have traced the wire to the ecu. As you look at the ecu it is the left hand plug. At least the cable with the same colour code goes there. Just to double check I traced the high speed return to the same plug and that has continuity unlike the low speed cable. So its decision time. Anybody have any idea how to remove and replace wires from these plugs?

 

[storeman]

Come on guys. No electricians among you?
Anyway I reckon I have traced the wire to the ecu. As you look at the ecu it is the left hand plug. At least the cable with the same colour code goes there. Just to double check I traced the high speed return to the same plug and that has continuity unlike the low speed cable. So its decision time. Anybody have any idea how to remove and replace wires from these plugs?

If it was mine I would temporarily splice a cable close to the ecu connector and also at the other end so it is in parallel with the original cable and try testing it first. If the fan runs then make the change permanent. I've never had any need to remove cables from the ecu plug so have no idea what's involved but as a last resort you could cut the cable and solder the new cable and seal with a couple of heat shrink tubes, one insulating the join with a slightly larger diameter and longer length adding additional electrical insulation and extra moisture protection.

 

[madbadandold]

I bought a kit a couple of months back and all it consists of is a load of different leads that allow you to check pins in the plugs. Magic it is.Over100 different leads. If anybody is interested I can give you details of the kit with photos! One of them is a fine needle that I used to check for continuity in the cable starting from the fan control plug disconnect point and worked my way up the loom. This meant of course undressing the loom of its tape, fastenings and conduit and hey presto I found the point of failure. It was right by the ABS controller where the loom to the top divides into two. Unwrapping it and found dirt that was in there because they had not taped the conduit the whole length and there was a lot. The loom was wound with cloth tape and that was damp too.The ABS plug was nice and clean as the cover had done its job. Anyway the wire had a kink in it but the outer sheath was intact. I cut the wire and inline crimped it and tested on Global and all is well. Well nearly because it still has not cured the limp mode!! The only message in the ECU now is "the glow plug is permanently powered"! I am not a happy man. The census is that the glow plug fault would not cause limp mode but I have checked everything else that could. Anybody know the wiring circuit to the relay i.e. there is two big cables and of course the plug to the glow plugs as I want to check it out.

 

[WillNZ]

I tested my one 407's fan yesterday with Diagbox [V7.62] while trying to find where I could do an adaptive reset... know I saw the option somewhere in an earlier foray when trying to diagnose issues with it's auto box, but still cant re-find it... So I was testing all sorts of things just because I could...

I was given 2 options, low speed test and high/low speed test. Trying the low speed test, no action at all from the fan. Aarrrghhhhhh!!!

However, then trying the high/low speed test I got a positive result with the fan alternating between high/very high and low speed in a sort of a random sequence, so assume all is ok with my fan despite no action from the low speed test option. Maybe your test option is the same?? ie not working on the low speed test option for some reason like mine did?

 

[madbadandold]

WillNZ see my post above yours. Thanks for the thought though

 

[reliable406]

You could be right as planet has tests for options not every car has and 206s for example have 3 different types of fan so the test for each could be different.

 

[WillNZ]

Cool. Obviously I was busy typing while you were also. Happy [fan] result.. :thumb:

 

[WillNZ]

Unfortunately most of the diagrams I have in my SEDRE for the 307 are schematic, I don't seem to have any detailed diagrams so can't help with the glowplug saga.

 

[madbadandold]

WILLNZ I have just uploaded service box and serde and mine is the same. Jimmymarsbar has said to try loading the SVG option which is down the side of that page where you have got the selection of chapters to view. I have but I have to restart the computer to see if it has loaded.

 

[madbadandold]

I tried restarting but no link. keeps saying something is running blah blah etc.

 

[madbadandold]

Looking at the Schematic Block electric diagram in Serde for the power unit shows that the preheat control unit(glow plug relay) has two feeds. One cable from the battery (yellow/red)and the other(yellow) from the BM34 unit(engine slave unit 34 fuses).
The BM34 is linked by a cable to the BSI1 unit.
Also there are three comms links.
1. BM34 links to BSI1 & CV100(controls under the steering wheel) by a Vancar1 link
2. BSI1 is also linked to the ECU by a CAN IS link
3.BSI1 is also linked to the inst. pnl & MFD pnl by a Vanconf link
So I assume a fault in the glowplug relay is picked up by the BM34 unit and transferred to the BSI which both sends it to the ECU and the inst pnl and the MFD pnl.
Central to all of this is the BSI. But the dilemma exists as The only fault shown on the ECU is this relay permanently energised does these communications show that it does trigger limp mode?

 

[reliable406]

I have said before you are barking up the wrong tree most HDI engines have the glowplug fault and still run fine you rarely see 1 without this fault !!

My sons 406 has NO glowplug relay still drives fine !

 

[madbadandold]

Yes I might be but I have ran out of trees!!
So the results of this evenings plat(it finally stopped raining) are as follows:
With battery connected but no key in the Ignition. Yellow/red cable battery voltage as it is a straight feed from the battery via the connection on the tray of the BM3.
yellow cable no voltage.
Key in and turned to on position with eng not running:
Y/R battery voltage
Y 8 volts
With engine running:
Y/R alternator voltage 14.2
Y 10 volts
Now this stayed like that as long as the engine ran. I would have thought that it would be a timed sequence to power the plugs but as the ECU reported it stays powered.
Switch engine off and down pops Y to 0 volts.
Rechecked the glow plug resistance and there are 2 @110 ohms, 1 @ 20 ohms and 1 open circuit.
So even though it might not fix the limp mode it is defective and to have no messages means the last resort is to have the ECU checked.

 

[jimmymarsbar]

I think the best thing to do now you've ran out of trees is to take a step back and give everything a once over again. It's bizarre that you're unable to find anything wrong and the car is in limp mode.

Can you get live data and post the findings? You might need more software for this (yes, more.......), such as AutoScreenRecorder. It'll record everything on your screen as a video file, and the forum can look at the live running data and digest everything that's happening.

The problem with fault codes is that they only appear when a variable is outside of a set parameter. However, a variable can be within the limits and still be causing problems. So a fault code may not be created in the ECU, but there still may be running issues. We have a 307 1.6hdi at work with a knackered turbo (caused by lack of care and maintenance). The turbo doesn't work any where near as it should, as the impeller is loose, yet no fault codes are stored. None of the sensors are picking up the lack of air flow from out of the turbo

I seem to remember you've done a vacuum test, and have eliminated leaks from the vacuum system. You don't have a DPF, which leaves the cat, EGR, air supply, turbo and fuel.

Does the engine/injection ECU show signs of water damage?

Just had a thought....... Get the engine up to operating temp and try the voltages again. Perhaps the engine is cutting back on power as the glow plugs are continuously heating the engine.

The general consensus is that the engine can run perfectly well without glow plugs, but perhaps there's something in the software telling the car to power down if there is a continuous supply to the plugs. If the engine is trying to cool itself down by opening the stat etc. when it is at temperature, but the plugs are contradicting this command, maybe it's self-remedying by going into limp mode.

I could be barking up the wrong tree myself, but more often than not you hear of glow plugs failing, and not overworking! Try unplugging the glow plug relay and see what happens (if you haven't already done so).

 

[madbadandold]

Jim thanks for your detailed post. yes I have checked every system.
The list is;
1. Cat checked for blockage. None
2. Egr valve and pipes removed and checked All clean and the valve works with suction and all the vacuum pipes were checked and no leaks found. I replaced the valves electrical controller.
3.Throttle peddle was swapped to check the potentiometer. All ok so original refitted.
4. Replaced the clutch switch with new one. Still the same.
5. Had the car at Lucas diesel specialists who confirmed all parameters of the fuel system are OK.
6. Cooling fan problem fixed.
7. Since getting pp2k I was able to view live data and all parameters were OK
A couple of times the car was out of limp after starting but after a few minutes it went back to limp.
I know the census is the glow plugs are not the cause they do have a purpose on this eng when its a really cold start for the pollution control. Like you Jim I think it is the cause at this time. I went on the ebay hoping to buy a new one but all that was there were second hand. I have ordered one @ £9.99 so that wont break the bank. Meanwhile I am going to replace the original and not connect the yellow cable.

 

[jimmymarsbar]

On my Megane, the car starts and runs much better when the glow plugs are functioning normally, so I'm not a big fan of people saying that glow plugs aren't required for modern diesels.

I do absolutely understand that a modern diesel can run perfectly well without the glows, but in my own experience, they are there for a reason and should be treated with the same level of maintenance as any other component.

I've never heard of a car shutting the power down due to glow plugs, but I wouldn't eliminate it as a possibility, if there's a permanent live feed to them whilst the engine is hot.

 

[madbadandold]

Jim I have removed the relay completely and no different so the fault is a hard fault in the ecu and so I am sending the ecu off for testing/repair.

 

[jimmymarsbar]

That would be my conclusion too. I think it's fair to say you've done everything possible to diagnose the fault!

I've (tried) to help a chap before with his 1.4 206 and he had an issue where the MAF sensor would trip the engine - it ran fine without the MAF (other than it was in limp mode), but as soon as the MAF was plugged in, the engine switched off, and there were all sorts of codes relating to impact detection, clutch switch and other totally unrelated faults.

Inspection of the looms showed no signs of shorting or arcing, so the only conclusion was that the ECU was damaged. The location of the ECU on the 206 was immediately below the top suspension mount, and you could clearly see where water was running down and on to the ECU.

Maybe it's cheaper getting a second hand, known-working ECU and BSI?

 

[madbadandold]

There are a number of problems of getting another known good one. You cannot trust the scrappies as they would say yes whatever and then you have to code it to the car. Anyway it is on its way now. £45 if no fault found then whatever if they find owt and how difficult it is etc. I will keep the forum updated as and when. Thanks for your help Jim.