C5 four-speed auto problems
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  1. #1
    Tadpole
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    Icon5 C5 four-speed auto problems

    Just acquired a 2004 C5 wagon which has already had transmission replaced about 2008. Now on 95,000km and it's saying "auto gear fault" and going into limp home mode. Need to stop, switch off and restart to get up into fourth. Citroen dealer can't pin down an exact fault and just says it needs a reco transmission, for megabucks. Other suggestions are faulty valvebody??
    Gear changes are a little clunky, but otherwise seems OK except when the fault comes up and locks it out of top gear.
    Any clues, please?

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  2. #2
    Fellow Frogger
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    Search the forum about the AL4 gearbox as it's been discussed often enough. You may get away with changing the pressure modulation electrovalve (on the valve block - half a day to get at and involves new oil too. Guess $1K), but then you may not and have to do the whole gearbox job anyway.

  3. #3
    Fellow Frogger!
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    Assume nothing, check everything, even a battery which is not up to scratch, tho it may turn the motor over ok, will trigger the ECU. A voltage loss of less than 2 volts is all that's required. It's a greatly overlooked fault with these transmissions. The fact that the ECU can be reset immediately should tell you to start looking for an external fault rather than internal. It's worth a try at anyrate, and check the forums although most will mention changing the electro valves. But you must change the oil if you do fix it. Best of luck.

  4. #4
    Fellow Frogger!
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    Just adding something which you may find helpful. At 40000 ks my C5 trans had valve and ECU updates. At 60000 Ks the trans was replaced. It lasted 800ks before the limp home mode in Syd peak hour [causing some very unkind words from Syd siders about banana benders and French cars]
    So after coming home I attacked that shocking Citroen wiring [no pun intended] and changed the oil. They must have used S/H oil when they rebuilt the box, if indeed it was rebuilt. I have my suspicions. I've now done another 37000 with no trouble. The trouble i've found with the wiring, I've posted before on this, lies in the silly peg type terminals [first seen around the 1900s on trains I believe] causing voltage loss and sometimes arcing due to unrestrained movement, coupled with a bad crimping method. Very hit and miss and, in my opinion is the main cause of a lot of the C5s many electrical faults . Folks report about limp home mode happening after turning a sharp corner or taking a bend a bit fast, or in stop start traffic. I say this is caused by movement between gearbox and chassis mounted ECU and by acociated wiring running through a very poor fuse box connector system. There is a fuse box update, uou might try for it. I haven't. Cheers

  5. #5
    1000+ Posts Greg C's Avatar
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    Change the oil. There are instructions on how to do it. Do it a few times and you may fix the problem. I am surprised the dealer was not able to find a fault logged in the system. The most common fault is the pressure regulation solenoid, not that difficult or expensive to fix as reported by David S
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  6. #6
    Fellow Frogger!
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    Not all faults are saved in the ECU memory, my own C5 never once recorded a trans fault despite having done many a mile on the back of a tow truck. It's mainly up to the experiance of the mechanic, [sorry automotive technician] at the dealership to interpret. As my bill once for a $1200 sensor plus $5 for a new bit of wire to connect it. The ECU had recorded a fuel rail pressure fault. But I leave you to savor that. See my other post. Broken mechanical parts, stay broken they don't fix themselves.
    Last edited by shanadoo; 25th January 2012 at 04:23 PM. Reason: missing explantion

  7. #7
    1000+ Posts Haakon's Avatar
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    Quote Originally Posted by shanadoo View Post
    Just adding something which you may find helpful. At 40000 ks my C5 trans had valve and ECU updates. At 60000 Ks the trans was replaced. It lasted 800ks before the limp home mode in Syd peak hour [causing some very unkind words from Syd siders about banana benders and French cars]
    So after coming home I attacked that shocking Citroen wiring [no pun intended] and changed the oil. They must have used S/H oil when they rebuilt the box, if indeed it was rebuilt. I have my suspicions. I've now done another 37000 with no trouble. The trouble i've found with the wiring, I've posted before on this, lies in the silly peg type terminals [first seen around the 1900s on trains I believe] causing voltage loss and sometimes arcing due to unrestrained movement, coupled with a bad crimping method. Very hit and miss and, in my opinion is the main cause of a lot of the C5s many electrical faults . Folks report about limp home mode happening after turning a sharp corner or taking a bend a bit fast, or in stop start traffic. I say this is caused by movement between gearbox and chassis mounted ECU and by acociated wiring running through a very poor fuse box connector system. There is a fuse box update, uou might try for it. I haven't. Cheers
    I wonder if you could elaborate on which terminals blocks were the problem, and how you repaired the pins for a reliable connection?

  8. #8
    Fellow Frogger!
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    Quote Originally Posted by Haakon View Post
    I wonder if you could elaborate on which terminals blocks were the problem, and how you repaired the pins for a reliable connection?
    Do the lot. Peel off the tape wrap for about 300mm, zip ties won't hold over this stuff. Make sure all terminals are clean and bright. Zip tie all the wires on each block together to form a seperate harness so they're going straight down into their respective blocks, tie about every 50mm. You should have about three seperate looms by now, then strap all these together, without pulling them out of alignment, all the way to where they come from the engine and tie them to the ECU box with a couple of heavy ties. There are holes to feed the ties through in the ECU box for this. You may need to bend/flatten the the harness down to get the cover back on, but the idea is to prevent any harness movement when the motor moves or from body flex. Those push loc terminal blocks are really bad news. Hope you can understand this description.

  9. #9
    1000+ Posts Haakon's Avatar
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    Quote Originally Posted by shanadoo View Post
    Do the lot. Peel off the tape wrap for about 300mm, zip ties won't hold over this stuff. Make sure all terminals are clean and bright. Zip tie all the wires on each block together to form a seperate harness so they're going straight down into their respective blocks, tie about every 50mm. You should have about three seperate looms by now, then strap all these together, without pulling them out of alignment, all the way to where they come from the engine and tie them to the ECU box with a couple of heavy ties. There are holes to feed the ties through in the ECU box for this. You may need to bend/flatten the the harness down to get the cover back on, but the idea is to prevent any harness movement when the motor moves or from body flex. Those push loc terminal blocks are really bad news. Hope you can understand this description.
    That all sensible. Its going in for the transmission guys to have another go at solving the converter unlocking problem - if that fails again, I'm going to do this before I scrap the car (its an 03' Xsara, but same EW10/AL4 drivetrain).

    Will remove as much/many of the looms as I can, and spend some evening with a mulitmeter testing wires. Your point about movement of the loom is a very good one!

  10. #10
    Fellow Frogger!
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    Quote Originally Posted by Haakon View Post
    That all sensible. Its going in for the transmission guys to have another go at solving the converter unlocking problem - if that fails again, I'm going to do this before I scrap the car (its an 03' Xsara, but same EW10/AL4 drivetrain).

    Will remove as much/many of the looms as I can, and spend some evening with a mulitmeter testing wires. Your point about movement of the loom is a very good one!
    And I might add, well proven on 4 other C5s that I've done now, providing you stop any movement between the CPU connectors and the harness. Be careful using the meter, the computer doesn't like it because of the backfeed, and you might trigger a fault reading.

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