208 1.2 petrol wont rev over idle

[tmead]

I've just acquired a tatty and unloved 208 for my son. It does start, but the idle is really lumpy and the accelerator does absolutely nothing, no response at all.

I'm also a bit suspicious that the fan continues running after switch off. I'm not quite sure why, as the engine is not hot, and the dash temp guage reads still pretty low.

I havent had a chance to plug in yet, but will grab codes etc at the weekend. The service light and the EML are on, and due to low battery (I think) the ABS light popped up too.
Like a Christmas tree !

I'm suspicious of something electrical, and did read somewhere about poor earth for a sensor on the throttle body causing a complete throttle response failure like this. I'm assuming that it may have a throttle cable and a throttle body somewhere - or are these completely drive by wire? I'll pop covers off and have a poke around at the weekend, just to check its nothing silly that has come loose, and I'll check as thoroughly as possiblke for chafed wires etc too. Everything car wise that I've dealt with over the last 10 years has been diesel, so I'll have to dig back out my petrol memories!

The cam belt looks rough on the rear surface through the oil filler, but I was expecting to change that anyway. I'll drain it and have the sump off to check the pickup is clean, and recommendations are to look at the valves for the variable timing and the vacuum pump to check for belt debris.

All suggestions welcome !

Tim

[tmead]

I'd hoped that this was engine related, and even resigned myself to possibly needing to swap it out. Not so sure now.

Diagbox will connect to the car, read the VIN and talk to the BSI, but it fails to recognise the ECU, ABS control unit and several others.

Even unrecognised, I can read the ABS unit and it shows an error that with a failure to communicate with the ECU. The airbag control unit shows a can + voltage error and speed error - I'm assuming those are supposed to come from the ECU ?

I tried all the options suggested fro connecting to the unrecognised ECU, and none connected. I have a cheap bluetooth dongle somewhere. If I can find that I'll pop it in and see if it will read the ECU faults.

I popped the variable timing solenoids out and there were some bits on the screens, so I think its likley that the cambelt is breaking up and the pickup may be clogged. I'm reluctant to fret too much about that until the ECU will chat though !

Any suggestions for where to look for sources of CANbus errors ?

[Paul-R]

What year is the car and what version of Diagbox are you running?

[tmead]

thanks @Paul-R,
car is on a 63 plate
Ive tried diagbox 7.83, which is my goto, and 7.05, just as a desperate measure
the lexia is a full chip that has communicated successfully with a 2014 dispatch/proace and a 2016 306, so the diagnostic hardware and software has had some success !

I'll check it still is able to communicate with the 2014 dispatch in a while.

[tmead]

Not much spare time to investigate, but I have plugged a cheapo dongle in and reset faults using torque. That left me with these that wont clear :
p0326
b0526
p2122
p2685

I also popped the plugs out, and #2 was wet with petrol and the insulator was very clean. The other two had tan tips but quite black insulators. Looks liek there may be a duff coilpack, but no code for that. I've got a coilpack from a 1.2 turbo unit around here somewhere that had an intermittent fault. If I can find it I'll stick that in and see if it runs any better.

Tim

[tmead]

Just wondering is anyone has access to schematics to help with identifying why the throttle doesnt do anything ? Theres a bunch of wires in both the accelerator pedal and throttle body connectors, so I am going to have a devils own job trying to figure out which is which !
I assume that basically theres a ground and a reference (probably 5v) and then moving the accelerator changes the voltage on another wire. I'm a bit lost by the presence of other wires - maybe related to cruise control etc ?

[tmead]

Swapped a replacement coilpack onto number 2 last night - didnt seem to massively improve things, but I think the battery may be fading, as it only coughed and spluttered and then died. Still no throttle response, so I can't wake it up that way.
Little time until after the weekend now.

[tmead]

Contemplating buying a replacment ECU and BSI set just to see if it makes any difference. I'm assuming i can swap the chip out of the key like previous models to avoid needing to change locks.

[GiveMeABreak]

Don't go replacing anything yet, there will be specific reasons for many of these faults. Let me have your VIN and I'll see what I have on these faults (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).

[tmead]

Thanks @GiveMeABreak I'll sort the VIN and try to post this evening - I'm supervising a bunch of scouts at an archery camp this weekend, so am a bit busy !

Its likley to be wiring I suspect, but that could be a bit of a nightmare to track down. I've heard horror stories about BSI loosing its marbles, but after 15 years of Citroen and Peugeot I've not had to even reset one, despite numerous flat batteries and disconnection for all manner of reasons ! This is the first ECU that I havent been able to communicate with at all from Pug / Cit software.

[GiveMeABreak]

Highly unlikely to be honest, those codes will be the key indicators and you want to avoid unnecessary expense in time and money if the faults are pointing to something specific. I'm thinking motorised throttle assembly / knock detection - but I'll await for your VIN to relate the codes specifically to your engine management system.

[tmead]

Thanks for the reassurance, I've never been keen on the swap parts until it works approach!

VIN is VF3**************[VIN obfuscated, can be read by forum staff]

[GiveMeABreak]

Ok, so here you go:

Fault Code:	P0326
Description of Fault:	Knock detector signal: Coherence. No signal received from the knock sensor.
Conditions for Fault to clear:	At least one of the following conditions must be fulfilled: - With the engine running - After switching the ignition off and then back on: When the ECU goes to sleep
Downgrade Modes whilst Fault is active:	-
Symptoms:	Lack of power Crackling / Sputtering / Knocking
Suspect Areas:	Electrical harness between the following two components: - Engine ECU - Knock sensor Knock sensor

Fault Code:	P2122
Description of Fault:	Motorised throttle position sensor signal: Short circuit to earth or open circuit on signal 2. The motorised throttle position value read by the sensor n°2 is higher than a threshold.
Conditions for Fault to clear:	At least one of the following conditions must be fulfilled: - With the engine running - After switching the ignition off and then back on: When the ECU goes to sleep
Downgrade Modes whilst Fault is active:	Deactivation of the canister purge function. Limitation of engine speed Motorised throttle housing in the back-up position Deactivating the cruise control Torque limitation Activation of the fan assemblies
Symptoms:	Absence of automatic stopping of the internal combustion engine. The cruise control and speed limiter do not work
Suspect Areas:	Electrical harness between the following two components: - Engine ECU - Motorised throttle unit Motorised throttle unit

Fault Code:	P2685
Description of Fault:	Sensors 5 volt supply: Motor-driven throttle position sensor (Pedal sensor voltage). The supply voltage 3 is higher than a maximum threshold or lower than a minimum threshold.
Conditions for Fault to clear:	At least one of the following conditions must be fulfilled: - With the engine running - After switching the ignition off and then back on : When the ECU goes to sleep
Downgrade Modes whilst Fault is active:	Activation of the fan assemblies Limitation of engine speed Natural opening position of the motorised throttle housing
Symptoms:	Lack of power Absence of automatic stopping of the internal combustion engine Banging/knocking/creaking
Suspect Areas:	Electrical harness Engine ECU

So I'd look at the knock sensor first of all and check the connections / consider replacing the sensor before looking at the other faults. According to the first fault code there is no signal being received from the knock sensor, so this is a good place to start and may also be having a knock-on effect causing other faults.

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[ozvtr]

The knock sensor is on the "back" of the engine and is only accessible from under the car.
The subframe and the RH drive shaft get in the way!
I worked on a 207 with this Puretech engine..Oh Boy! The ape who worked on it before me smashed nearly every electrical connector on the engine!! Including the knock sensor connector! I don't know how. Access to the knock sensor is VERY limited. I was not able to repair the connector.
Being plastic and on a hot engine the electrical connectors get very brittle, so be very careful when working on them!

[ozvtr]

I'm also a bit suspicious that the fan continues running after switch off. I'm not quite sure why, as the engine is not hot, and the dash temp guage reads still pretty low.

The 207 that I worked on also did this randomly. Had to pull the battery +ve to stop it running. Sorry but I didn't find a fix, it just magically stopped doing it.