C4 Grand Picasso 2006 does not start until battery disconnected and reconnected

[Agreeable7793]

Hi all! I'm trying to diagnose an injector/gearbox issue with my 2006 Grand Picasso. I believe it is due to ECU communication or some other electronics, but I'm looking for suggestions.

The story goes as follow:

1. Since a couple of years the automatic transmission would randomly stop working, meaning I could not change gear while going. Turning the car back off and on again would fix it, and it was sporadic enough that I didn't really care to look that much into it. Local dealer was also unable to diagnose.
2. A month ago while on a relatively long trip, the dashboard lit up like a Christmas tree and I lost control of the gears again, but this time the brakes were also unresponsive. I tried turning off and on again, but the car would not turn back on at all. The dashboard stayed off and the engine did not start.
3. After getting towed and exploring my options a bit, I tried disconnecting the battery. Surprisingly, after reconnecting, the car started back on without a hiccup and without any service lights.
4. The car did the same again as 2. while on the highway (first time was regular road ~80km/h, this time highway ~130km/h), again not turning on after getting turned off. I disconnected and reconnected the battery and was able to continue my trip.

The car still drives fine when not having this issue, and I've driven it quite a bit more since, so I cannot replicate the issue at will.

Now, I went back to a local mechanic to get the error codes:

1. Automatic transmission Marelli CFC300P:
   - P0944 Hydraulic Pressure Unit Loss of Pressure
   - U1208 No communication with engine ECU
2. EDI Injection Siemens SID 803
   - P2562 Turbo position copy signal fault
   - P1404 2 additional heating and preheating circuit
   - P0470 Pressure diff. in exhaust
   - P0337 Engine speed signal: Signal not coherent
   - P1403 Additional heating circuit
   - P1351 Pre-post heating relay
3. Suspensions WABCO
   - P0562 ECU undervoltage
4. BSI Johnson Controls
   - U35FF ECU BSI Internal Fault Not Characterised
   - B3998 Headlamp washer

Given the plethora of things seemingly wrong and the fact that the car still runs perfectly fine when reconnecting the battery, it looks plausible to me that all of them are connected to some ECU/connection fault. Perhaps high temperature, or vibrations, are dislodging an already precarious header or wire and cutting off communications. Local dealers and mechanics are quite unwilling to work on the automatic transmission/electronics in general, so I am trying to get this diagnosed by myself.

I will start by checking the fuses as soon as I have some spare time, but if you guys think I'm completely off base or have some better ideas I'm all ears.

Thanks a lot!

[GiveMeABreak]

Please post your VIN in full without spaces - it will be automatically masked from public view after submitting your post & will only be visible to staff.

[Agreeable7793]

Here it is: VF7**************[VIN obfuscated, can be read by forum staff]

[GiveMeABreak]

Ok, so the first thing to get right is this does not have an automatic transmission. It has a manual gearbox and clutch, with piloted actuators to do the gear and clutch changes, so no torque converter - it's a piloted manual gearbox.

Fault Code:	P0944
Description of Fault:	Fault: oil pressure storage cell discharged : Not characterised Description of the diagnostics: Discharging of the hydraulic accumulator Context of appearance of the fault code: The following conditions have to be met: - Clutch closed - Absence of gear changing Technical precision on the context of appearance of the fault code: Operation of the hydraulic pump Supply voltage correct between 8V and 16V (Pin 3 of the 28-way connector)
Conditions for Fault to clear:	Ignition switched off and on again
Downgrade Modes whilst Fault is active:	Change to Neutral and anticipated closing of the clutch ( engine running - Gear engaged - Clutch open)
Symptoms:	Lack of power Leaks
Suspect Areas:	Electric motor Electro-pump Level of oil in the gearbox hydraulic reservoir Accumulator Pressure sensor Leak/kinking in the hydraulic piping Controlled manual gearbox ECU

Fault Code:	U1208
Description of Fault:	Fault in the information transmitted by the engine management ECU: Value received incorrect. Description of the diagnostics: No information sent by the engine ECU (Foot throttle pedal ; Engine speed ; engine torque) The time of appearance of the fault code is 1s Context of appearance of the fault code: The following conditions have to be met - Ignition on - The starter motor is not operating Technical precision on the context of appearance of the fault code: Supply voltage correct between 8V and 16V (Pin 3 of the 28-way connector). Absence of fault codes U1000 - U1003 - U1108
Conditions for Fault to clear:	Reception of 20 consecutive items of valid information
Downgrade Modes whilst Fault is active:	Possibility 1 Engine speed fault - Change to neutral and no gear can be engaged - Opening of the clutch when close to idling speed - Take-off deactivated (With the vehicle stopped) - If the vehicle has the Stop and Start system : Stop and start function deactivated Possibility 2 Accelerator pedal position fault - Automatic mode deactivated - Change to neutral and no gear can be engaged - Opening of the clutch when close to idling speed - Take-off deactivated (With the vehicle stopped) Possibility 3 Fault with engine temperature and torques - Gear engagement downgraded - Crawling deactivated Switching on of the warning lamp and/or warning message (*) If there is a fault on the information on accelerator pedal position or engine speed "SERVICE" warning lamp Sport warning lamp Snow warning lamp Automatic or 6-speed piloted manual gearbox warning lamps (Orange PRND triangle) Display of a "-" on the fascia panel
Symptoms:	Possibility 1 Engine speed fault - Automatic mode deactivated - Change to neutral and no gear can be engaged - Take-off deactivated - Difficult/impossible to change a gear Possibility 2 Accelerator pedal position fault - Automatic mode deactivated - Change to neutral and no gear can be engaged - Take-off deactivated - Difficult/impossible to change a gear Possibility 3 Fault with engine temperature and torques - No customer complaint
Suspect Areas:	28-way harness of the piloted manual gearbox ECU Engine ECU

(*) According to equipment and engine.

Fault Code:	P2562
Description of Fault:	Turbocharger solenoid valve repeat signal. Value below the reference value (repeat sensor local loop difference). Conditions of activation of the diagnostics DW10B, DV6: engines: Engine running: The position repeat must be 30 % higher than the reference value for 5 seconds
Downgrade Modes whilst Fault is active:	DW10B, DV6 engines: Stopping of the regulation of the variable geometry turbocharger
Symptoms:	-
Suspect Areas:	The other fault codes must be rectified first. Check of the creation of a vacuum and of the sealing of the vacuum circuit - vacuum pump - Pipes Check of the control of the turbocharger regulation solenoid valve - Breather pipe (Solenoid valve ) - Electrical harness between the ECU and the solenoid valve - Solenoid valve 12V supply Check ( turbocharger) - Turbocharger variable geometry points of resistance - Sealing of the vacuum capsule - Vacuum capsule rod Appropriate tools: Vacuum pump Ruler "T" union Adaptor harnesses (4229-T / 4340-T) Controlled terminal box (in manual mode) or manual terminal box Engines concerned: DV6 E4 without particle filter (9HY), DW10B

Fault Code:	P1404
Description of Fault:	Additional heating 2 fault: Circuit to earth ; Short circuit to positive ; Open circuit ; Actuator malfunction. Description of the diagnostics: Short circuit to earth or short circuit to positive or open circuit: Actuator malfunction (For at least 2 seconds) Conditions of activation of the diagnostics: Battery voltage more than 7V No error on BUS internal to the engine management ECU
Conditions for Fault to clear:	Ignition on
Downgrade Modes whilst Fault is active:	-
Symptoms:	The passenger compartment heating is considerably degraded
Suspect Areas:	Additional heating element Connector Relay Electrical harness Engine ECU

Fault Code:	P0470
Description of Fault:	Exhaust differential pressure sensor signal: Differential pressure coherence on starting. Description of the diagnostics: The particle emission filter measured differential pressure is higher than a threshold for 2 seconds. No active regeneration of the particle filter after 8 hours with presence of a fault: Differential pressure sensor; Clogged particle filter. Conditions of activation of the diagnostics: The following conditions have to be met: - The temperature downstream of the catalytic converter : Between - 100 and 600 ° C - No fault on the particle filter differential pressure sensor
Conditions for Fault to clear:	Ignition on
Downgrade Modes whilst Fault is active:	Downgrade ASR mode (Torque limitation for traction control). Deactivation of the speed limiter. Deactivation speed limiter until the next time the ignition is switched on. Deactivation of the cruise control. Deactivation cruise control until the next time the ignition is switched on. The engine ECU limits the fuel flow. Switching on of the warning lamp and/or warning message: Warning lamp MIL.
Symptoms:	Lack of power
Suspect Areas:	Pneumatic by-pass meter Turbocharger air cooler Particle filter Particle filter differential pressure sensor Hoses Electrical harness Connector

Fault Code:	P0337
Description of Fault:	Engine speed signal: Signal not coherent. Description of the diagnostics: Incoherent number of teeth on the target of the engine speed sensor Conditions of activation of the diagnostics: No long tooth on more than 6 CAM heads (No. of heads arising from the camshaft sensor signal to confirm the synchronisation with the crankshaft sensor (TDC)).
Conditions for Fault to clear:	Under starter
Downgrade Modes whilst Fault is active:	Cutting of the injection if there is a resynchronisation failure
Symptoms:	Starting problem
Suspect Areas:	Engine speed sensor Engine speed sensor target Electrical harness Connector

Fault Code:	P1403
Description of Fault:	Additional heating relay control fault 1: Circuit to earth; Short circuit to positive; Open circuit; Actuator malfunction. Description of the diagnostics:/b] Short circuit to earth or short circuit to positive or open circuit: Actuator malfunction (For at least 2 seconds). Conditions of activation of the diagnostics: Battery voltage more than 7V No error on BUS internal to the engine management ECU
Conditions for Fault to clear:	Ignition on
Downgrade Modes whilst Fault is active:	-
Symptoms:	The passenger compartment heating is considerably degraded
Suspect Areas:	Additional heating element Connectors of the additional heating element Engine ECU Electrical harness Relay

P1351: is just Pre-heating relay circuit: Coherence - Relay supplied and glow plugs not supplied.
P0562: Battery voltage: Too low

The last 2, are non-descript BSI faults.

[Agreeable7793]

So then it would seem the first thing to check is the harness from the gearbox ECU to the main ECU. Do you have schematics for that 28pin connector?

[GiveMeABreak]

Here you are:

With the exception of the wiring codes, most of the component codes are indexed here:

PSA Electrical Diagrams - Wiring & Symbols Codes Index

Gearbox Wiring Layout


Wiring

[Agreeable7793]

Beautiful! Most of the 16xx components' descriptions are missing, but I kind of get what they are and it doesn't seem too relevant to know precisely either.