Hi all I hope someone can advice how to resolve this.
I have replaced an electric steering rack in C4 MK2 1.6bluehdi with second hand one and have an fault code U1221 81 stating ''No communication with power steering ECU'' I have used latest lexia diagnostics so believe the code must be correct.
Can someone advice if the new steering rack needs to be somehow coded or calibrated?
Any advice would be much appreciated thanks
Last edited by myglaren on 23 Jun 2024, 12:10, edited 1 time in total.
Reason:Falling-over images propped up.
All the C4 (b7) models I can see don't have electric steering fitted on the rack, they are pump driven. Do you have the VIN as I don't think this is a C4
Hi the vin is VF7**************[VIN obfuscated, can be read by forum staff] its 2015 it may be that I not plugged the yellow plug all the way in I will check today but is definitely electric as already swapped it.
No wonder I'm confused, you have a C4 Picasso MK II (B78) - a completely different vehicle to a C4 / C4 II, as these don't have electric power steering units on the rack unlike the MK II Picasso.
I would certainly be checking that the connections are tight and that there are no loose wires in the plugs or bad pins / connections.
Fault Code:
U1221 81
Description of Fault:
Communication with the power steering ECU: Data invalid. Value received invalid. The time for recording the fault code is 100 milliseconds.
Conditions for Fault to clear:
Ignition on (For at least 30 seconds)
Downgrade Modes whilst Fault is active:
Deactivation of the ESP function.
Switching on of the warning lamp and/or warning message: ESP warning lamp
Symptoms:
Switching on of the ABS/ESP/EBFD warning lamps with/without error message
Suspect Areas:
Electric power steering
Intersystem CAN network
PS: I've amended your Profile to state C4 Picasso to avoid future confusion.
Does the new rack need to be programmed? As when tried to calibrate wheel angle sensor it woudn't let me, any idea?
When gone to the steering whell ecu this are the faults ( see picture)
Do I need to remove the old rack ECU and stick it back on the new one or there is a easier way surelly.
That's why I asked if you had replaced it with the exact same part number from the exact same vehicle as it may well be configured differently. Yes they do require calibration if removed / replaced.
If your vehicle has semi-automatic parking assistance, then it will have an absolute steering wheel angle sensor fitted, as well as the standard steering column torque sensor. This is because when switched on, the power steering ECU has no idea with a torque sensor alone what position the steering wheel is at for leaving a parking space, so requires the absolute angle sensor located int he steering wheel.
As far as I can see, you don't have semi-automatic parking assistance, so won't have the steering wheel angle sensor, just the torque sensor. So this may be why there is no communication with it.
If the donor unit is from a vehicle that did have the semi -auto parking, then of course it will cause problems when fitted to your vehicle.
Also, are you 100% sure you haven't bought a broken unit.....
Hi Marc and thank you for your reply and explanation, I cant confirm if the rack was working I was told it came from a working car and mechanically works fine after fitting I just cant get the calibration done with the diagbox 7.58 , does it need to be done by citroen dealer? Or should I just swapp the old rack ecu and fit it to the new one....?
V7.58 was only released on 14th November 2014, your vehicle has a build date of 14th July 2015, so that may be an issue, and assuming you have a full-chip Revision C VCI of course.
You may need to update your Diagbox version, but no guarantees this will be the issue of course.
Keeping your old ECU may be the better choice, but whether the calibration will still be required I can't say. Officially this has to be done if removed / replaced.
Parking assistance ECU is separate, but the point I was trying to make is that the donor ECU may be configured differently for a vehicle with semi-auto parking, which will have a separate steering wheel angle sensor to operate in addition to the normal steering torque sensor for models without. So everything is inter-related as the Parking ECU gets it's data from the ESP ECU concerning the steering angle sensor, which won't be fitted on vehicles without semi-auto parking.
This may be why there are some anomalies if the existing configuration is set for options that don't exist, so is not getting expected data.
I have finally found the cause of steering rattle/play, its the rack tensionner under the motor as it has a lot of play on one side, managed to remove the motor and ecu and hopefully once swapped there should be no issues with communication.
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Last edited by Grzegorz22crewe on 24 Jun 2024, 20:38, edited 1 time in total.
