Gearbox ECU problem C4 pilotless gearbox

[Ceenine]

I have an error message on my Lexia (gearbox diagnosis section) which states "ECU + permanent supply open circuit". Does anyone know where I may get some advice as to what exactly is the problem. Would an ECU repairer be a likely help. The vehicle is a C4 1.6 HDI pilotless 6 speed gearbox of 2007 vintage. Problem caused by positive lead touching main ECU casing. Main ECU has been replaced. Gearbox will not engage.

I purchased a second hand ECU from a Qld (Aust.) wrecker recently which had heaps of errors on it. That is the risk you take.(same Magnetti Morelli model of 5 months difference in manufacture.)

Don W.

[xantia_v6]

Can you clarify which ECUs have been replaced?, you post is a little ambiguous.

If a heavy current has passed from the case of an ecu, it is likely to have damaged PCB tracks in that module,and perhaps others that are connected to the same earth circuit. Does the lexis now have communication with all important ecus?

[Ceenine]

I have replaced the main ECU and BSI. The Lexia shows the fault as described only. The diagnosis session brings up that fault in the gearbox ECU section. It suggests to me and I have no knowledge of electronics, that the spiking of the main ECU case has resulted in the gearbox ECU being affected. How does that happen?

I have tested that a 12 volt signal is being picked up at the connector channel 3 to the gearbox ECU .So obviously 12 volts is getting through. The Service Citroen manual that I downloaded states that "the negative terminal of the gearbox ECU is connected to the gearbox casing(earth), there is no channel allocated on the ECU connector." I note that channel no. 18 is "gear selector earth". I am not sure if that is the negative terminal that the above comment is referring to.

I further note that:
Channel 1 is designated "Input: ECU connector"
Channel 3 is designated "Permanent +12 volts"

So what does the fault message " ECU + permanent supply Open circuit" mean? It appears maybe that I need to replace the gearbox ECU?

Don

[Ceenine]

I note that my previous post does not make it clear that the Lexia is communicating with all ECU's.
Don

[wheeler]

might be worth removing the gearbox ECU & splitting it open to check for any visible damage to the PCB.

[Ceenine]

So what am I looking for when I split the ecu.

Do you know what the error message means. No-one seems to be able to tell me. If the nature of the error was to be elucidated I may have a chance of tracking the problem.

Regards from down under