Citroen C2 1.4 petrol VTR 2005 starting problem

[ozvtr]

The TU3Jp engines are notorious for head warping and head gasket leaks.
Check the spark plugs for signs of coolant on the electrodes. Or if there is any unexplained loss of coolant.
As Mick says try "starting fluid" to see if there is spark.
See if you can measure the fuel rail pressure. If you are really desperate you can use a tyre pressure gauge (your own, not the one at the service station!). Should be 35 to 40 psi or 2.5 to 3 BAR.
The injectors, fuel pump and coil pack are all on the same fuse. Ensure that fuse is OK.
In 2005 there were two versions of the C2. CAN-VAN and "all CAN". The CAN-VAN cars have 6 temperature LEDs. The all CAN cars have only one. If it's an all CAN car, the center display will tell the driver if there is a "security problem", I.E. a problem with the key. The CAN-VAN cars won't tell you if there is a problem.

[ovouti]

I did some recearch from the history of the car, car has been starting before the ABS unit was taken off. So I would assume its because there is no ABS unit that its not starting, I have used one coming. Ill install that and then try again.

[ovouti]

Hi, can I install used abs module? Do it need to be coded or something?

[wheeler]

If the ABS module is unplugged then the car will not start as the CAN lines will be open circuit. The ECU's on the can are 'Daisy chained' with the BSI & engine ECU being the end of the line at each end. by disconnecting the ABS unit you have essentially broken the comms between the engine ECU & BSI.
For testing purpose you can bypass it by bridging over the CAN H 'in & out' an the CAN L 'in & out'

[wheeler]

Hi, can I install used abs module? Do it need to be coded or something?

Yes you can, only basic coding needed like tyre size, gearbox type & engine type.
If you use an ECU of the exact same spec car the no coding would be needed.

[ovouti]

Hi, can I install used abs module? Do it need to be coded or something?

Yes you can, only basic coding needed like tyre size, gearbox type & engine type.
If you use an ECU of the exact same spec car the no coding would be needed.

Thanks!

[ovouti]

I got it running, I bought a used abs pump and installed that, deleted codes and its runs just fine. No coding needed. Thanks everyone for answers!

[wheeler]

Great news.
No coding is needed to allow starting but did you check other coding like tyre size?
If the pump has come off a model with a different tyre size the speedo may read incorrect

[ovouti]

No didnt check that, i will do that when i have right device to code that. Abs pump was from exact same car and model.

[ozvtr]

If the ABS module is unplugged then the car will not start as the CAN lines will be open circuit. The ECU's on the can are 'Daisy chained' with the BSI & engine ECU being the end of the line at each end. by disconnecting the ABS unit you have essentially broken the comms between the engine ECU & BSI.
For testing purpose you can bypass it by bridging over the CAN H 'in & out' an the CAN L 'in & out'

D'OH! I should have spotted this one.
Actually the ABS is on the end of the CAN BUS from the BSI. This CAN BUS includes the power steering module. The engine ECU and the gearbox ECU are on an extension BUS from the ABS module.
The BSI, power steering module and the ABS module are all on one harness and the parallel connection to the steering module ECU is in the harness. Just as the ABS, gearbox ECU and the engine ECU are all on one harness and the parallel connection to the gearbox ECU is in the harness.
I am not sure if the ABS module is just a node or it's a hub for the engine ECU BUS?
My guess is that the ABS module is a hub. That keeps the BUSes short and isolates engine and gearbox failures from the steering and ABS.

Either way, good catch!

[wheeler]

Im pretty sure the Engine & BSI are alwaysend of line (on both Full CAN & VAN/CAN)
On VAN/CAN systems if I remember right all the of the CAN ECU's are in series apart from power steering which is piggy backed off in parallel
I think Full CAN systems are the same

[ozvtr]

Im pretty sure the Engine & BSI are alwaysend of line (on both Full CAN & VAN/CAN)
On VAN/CAN systems if I remember right all the of the CAN ECU's are in series apart from power steering which is piggy backed off in parallel
I think Full CAN systems are the same

The "serious" ECU's were always CAN BUS (engine, ABS, gearbox, steering). VAN BUS was only used for the ancillary stuff, like the radio and aircon.
The ECUs on the CAN lines are in parallel...except for the terminators (I.E. the "ends"). The C2 and C3 CAN BUSes are very simple.

Here is a typical CAN BUS layout. A bunch of ECUs in parallel and terminators at either end.

Here is a "quick n dirty" schematic of the C2/3 CAN BUS layout.
You'll notice that the ABS module is literally in the middle of the CAN BUS and it is the only ECU with CAN in and CAN out. Why? It could just as easily be in parallel like the gearbox or steering ECUs!?
I postulate that it's a hub and it isolates potential CAN BUS problems. If there is a CAN BUS problem with the engine ECU or gearbox ECU, the steering ECU will still receive CAN data from the ABS ECU and continue to work! And, the BSI will still get speed data from the ABS module.
I have a spare ABS ECU and I'll see if it has terminating resistance on the in and out lines.

So to go back to the OP. Disconnecting the ABS module severs the connection between the BSI and the engine ECU. Causing the engine ECU to not run. However, disconnecting the steering or gearbox ECU's WOULD NOT stop the engine from running!

Now Wheeler spotted this...not me. I make no claim to that! As I said before, D'Oh!

[ozvtr]

I am really, really, really sorry if I am boring people with this post and have "hijacked" it. Sorry, sorry.

BUT the physical layout of the electrical wiring of the CAN BUS has befuddled me. I think the ABS module "sits" in it's position on the CAN BUS for a reason, because, from a physical wiring stand point, it makes no sense!
The CAN BUS wiring starts at the BSI in the cabin, then goes through the firewall to the steering ECU. OK so far. It then runs right past the engine ECU in the battery box, right past the gearbox ECU, all the way down to the front of the car, to the ABS ECU! It then turns on itself and goes BACK to the gearbox ECU then on to the engine ECU! Literally doubling the amount of wire required! Why?
I believe it's convoluted because of the reasons I gave in the previous post. It allows a safety margin.

Again, sorry for hijacking the post but this wiring layout thing was "sticking in my craw".

[wheeler]

I have a spare ABS ECU and I'll see if it has terminating resistance on the in and out lines.

I'm pretty sure there are no EOL resistance in the ABS
You can check this by measuring a perfectly working CAN bus line (60 ohms).
If you then disconnect the ABS unit & measure the CAN lines individually in the 'in & out' you will get 120 ohms each way. If there was EOL resistance in the ABS it would completely chance these readings.
This is how i normally start in depth fault finding on a CAN network that has a 120 ohm total resistance, By disconnecting the ABS & doing a resistance check I can rule out half the circuit, if you measure the 'in & out' you can see if the break is between the BSI & ABS or between the ABS & BSI effectively ruling out half the circuit.

[ozvtr]

I have a spare ABS ECU and I'll see if it has terminating resistance on the in and out lines.

NOPE. Turns out to be just a plain old node.

I'm pretty sure there are no EOL resistance in the ABS
You can check this by measuring a perfectly working CAN bus line (60 ohms).
If you then disconnect the ABS unit & measure the CAN lines individually in the 'in & out' you will get 120 ohms each way. If there was EOL resistance in the ABS it would completely chance these readings.
This is how i normally start in depth fault finding on a CAN network that has a 120 ohm total resistance, By disconnecting the ABS & doing a resistance check I can rule out half the circuit, if you measure the 'in & out' you can see if the break is between the BSI & ABS or between the ABS & BSI effectively ruling out half the circuit.

If the ABS module was a bridge, It would have a 120 Ohm resistance across the "in" line and the same across the "out" line. Making two "mini" CAN BUS circuits. The in and out lines would not be directly connected. The bridge shuffles data between the two CAN circuits.
But the ABS module is not a bridge...just another node.