Technical punto not cranking, padlock out

[crawfie]

Hi All, I've just done a oil and filter change on my Fiat Punto grande 1.2 petrol 2007 but now it's not starting all the lights are on padlock light goes out, but when i turn the key there is no cranking or clicking just silent.I've checked the earth strap and even put a jump lead from the battery negative to the engine but still wont crank, any ideas. (it drove up my car ramps ok to do the oil change)

 

[crawfie]

UPDATE, ignition switch tested ok starter fuse is ok and both relays were bench tested and found to be ok car, i've removed the cover from the relay and the car will start if i manually activate the starter relay so at least its of the car ramps, tomorrows job will be to trace the wiring from the ignition switch and see if theres a break in tit

 

[crawfie]

car still not starting but i now have a code P0615, I've checked all the wiring both visually and with a multimeter all is good in that respect, if i put 12 volts on to the starter relay the car will crank and start, I'm now leaning towards either the BCM or ECU at fault. one strange thing that leads me to this is when checking the wire that sends the crank signal i was getting no voltage however when i cut the wire to see if it was the ignition switch i have 12 volts when i turn the key to the start position, splice the wires back together turn the key 0 volts, its the switch i hear you cry alas know i removed the plug from the switch and using jumper wires i had the same result

 

[AnthonyH]

It's difficult to follow what's going on without a circuit diagram. I'm interested in the problem but can't currently add anything I'm afraid.

 

[crawfie]

all wiring checked out ok , checked today with a multimeter, I'm not getting the 12v supply to the relay at the ecu even though all the wiring and earths are ok, car will start if i bridge out the relay, is like a signal from the bcm is it being sent to the ecu to say its ok to start

 

[bugsymike]

all wiring checked out ok , checked today with a multimeter, I'm not getting the 12v supply to the relay at the ecu even though all the wiring and earths are ok, car will start if i bridge out the relay, is like a signal from the bcm is it being sent to the ecu to say its ok to start

Your symptoms sound very similar to something I had several years ago on a 06 Fiat Grande Punto 1.3 MJ that I bought as a non runner after previous owners garage had fitted lots of parts and ended up damaging the timing chain by violently trying to tow start it, stupid really as with no fuel getting to engine they could have towed it to Scotland and it still wouldn't have started!.
The cause was the trigger wire at the fuse box for the fuel pump relay which also supplies a signal to the starter from the ignition switch.
So if you bridge the contacts at the relay socket the car starts, but even with a new relay it doesn't.
The trigger wire seems to supply a + or - signal to activate or not, the relay.
I had to flip the fuse box over and locate the wire to follow back through the loom across the bulkhead to the ECU.
Having found this I ran a new wire up to the ECU on the opposite inner wing and just where I was going to make the connection I found the original wire had rotted through a couple of mm from the ECU plug connection. When you gently pulled on the wire it appeared to stretch as only the plastic holding it together.
Let us know if helps.
This was about five years ago so I can't remember which contact wire at the ECU , sorry

 

[crawfie]

Your symptoms sound very similar to something I had several years ago on a 06 Fiat Grande Punto 1.3 MJ that I bought as a non runner after previous owners garage had fitted lots of parts and ended up damaging the timing chain by violently trying to tow start it, stupid really as with no fuel getting to engine they could have towed it to Scotland and it still wouldn't have started!.
The cause was the trigger wire at the fuse box for the fuel pump relay which also supplies a signal to the starter from the ignition switch.
So if you bridge the contacts at the relay socket the car starts, but even with a new relay it doesn't.
The trigger wire seems to supply a + or - signal to activate or not, the relay.
I had to flip the fuse box over and locate the wire to follow back through the loom across the bulkhead to the ECU.
Having found this I ran a new wire up to the ECU on the opposite inner wing and just where I was going to make the connection I found the original wire had rotted through a couple of mm from the ECU plug connection. When you gently pulled on the wire it appeared to stretch as only the plastic holding it together.
Let us know if helps.
This was about five years ago so I can't remember which contact wire at the ECU , sorry

thanks I'll have a look at the drawing on elearn and see if i can locate the feed

 

[crawfie]

FIXED KIND OFF
ok no broken wires found, still not got to the bottom of this, but what with bit of McGyvering Ive got the car running and starting of the key.

basically what I've done is bypassed the both the BCM & ECU by wiring in a separate relay for the starter circuit. one other thing i did notice when i did this was that the car would crank and crank but not fire but would fire if i left the original relay instiu also had to leave the starter wire from the ignition switch and bcm or again the car wouldn't fire

 

[bugsymike]

no broken wires found, still not got to the bottom of this, but what a bit of McGyvering Ive got the car running and starting of the key.

basically what I've done is bypassed the both the BCM & ECU by wiring in a separate relay for the starter circuit. one other thing i did notice when i did this was that the car would crank and crank but not fire but would fire if i left the original relay instiu

At least it is running, it may be like the one I mentioned before, that it feeds the fuel pump in the tank also, so by leaving the relay in it activates that circuit.

 

[crawfie]

I've had a multimeter on every wire between the bcm, ecu and fuse box did a couple dodgy looking wires but nothing broken and no open circuits now all i need to do is tidy the loom, the cloth tape that was around it fell to pieces when I touched it and was missing in other places.I used to hate these kind off faults in my profession as a domestic appliance eng. I did open up the relay because I'm nosey that way and there is a resistor across the supply and also 10 volts across the terminals when the car is running so it could well be a feed for the fuel pump

 

[bugsymike]

I've had a multimeter on every wire between the bcm, ecu and fuse box did a couple dodgy looking wires but nothing broken and no open circuits now all i need to do is tidy the loom, the cloth tape that was around it fell to pieces when I touched it and was missing in other places.I used to hate these kind off faults in my profession as a domestic appliance eng. I did open up the relay because I'm nosey that way and there is a resister across the supply and also 10 volts across the terminals when the car is running so it could well be a feed for the fuel pump

Did you locate the trigger/control side connections for that relay?
Unlikely to be the same fault but the symptoms are similar.

 

[crawfie]

Did you locate the trigger/control side connections for that relay?
Unlikely to be the same fault but the symptoms are similar.

I did yes i had no voltage on it at the ecu which leads me think the ecu is not getting the signal from the bcm

 

[bugsymike]

I did yes i had no voltage on it at the ecu which leads me think the ecu is not getting the signal from the bcm

On mine the wire was a direct feed from the ECU on o/s inner wing across bulkhead and into the bottom of the fusebox to the back of that relay.
When you located the wire was it possible to colour match it to the ECU?
Or carefully introduce a fused test wire to see if it would activate that relay?

 

[crawfie]

On mine the wire was a direct feed from the ECU on o/s inner wing across bulkhead and into the bottom of the fusebox to the back of that relay.
When you located the wire was it possible to colour match it to the ECU?
Or carefully introduce a fused test wire to see if it would activate that relay?

i could activate the relay if i put voltage on the wire at the ecu end with the ecu unplugged, but had no voltage coming out of the pin on ecu when i plugged the multi plug back in

 

[AnthonyH]

This is your circuit diagram. The diagram gives the colour of the wires, the colours aren't always accurate, but will be close, for example "RD" means a red wire. Based upon what i've read in this thread most likely the blue wire (pin 11) or the gray wire (pin 1) on the BCU are faulty. The BCU is hopefully fine, and if you look closely at those wires one of them will have a tiny tear...be sure to wear glasses if you need them and shine a torch on them to get proper light.

 

[crawfie]

This is your circuit diagram. The diagram gives the colour of the wires, the colours aren't always accurate, but will be close, for example "RD" means a red wire. Based upon what i've read in this thread most likely the blue wire (pin 11) or the gray wire (pin 1) on the BCU are faulty. The BCU is hopefully fine, and if you look closely at those wires one of them will have a tiny tear...be sure to wear glasses if you need them and shine a torch on them to get proper light.

View attachment 453941

many thanks for the diagram, Ive been using elearn to try and find the problem this diagram is easier to follow, not sure if its the correct one for my car as I've only 3 wires on my ignition switch my car is a 2007 punto grande 1.2 8 valve

 

[AnthonyH]

many thanks for the diagram, Ive been using elearn to try and find the problem this diagram is easier to follow, not sure if its the correct one for my car as I've only 3 wires on my ignition switch my car is a 2007 punto grande 1.2 8 valve

The diagram is taken from my Grande Punto Haynes manual and is for your exact model, engine and year.

Understanding the circuit diagram and how it correlates to the car is a difficult task. You could easily be doing this for several more days/weeks. Or you could pay an auto-electrician. I'm glad i don't have this problem.

 

[crawfie]

The diagram is taken from my Grande Punto Haynes manual and is for your exact model, engine and year.

Understanding the circuit diagram and how it correlates to the car is a difficult task. You could easily be doing this for several more days/weeks. Or you could pay an auto-electrician. I'm glad i don't have this problem.

im well used to reading circuit diagrams used them a lot in my 40 years as a domestic appliance engineer,

 

[crawfie]

these is the ones I've been using, which correlate with my car

 

[AnthonyH]

these is the ones I've been using, which correlate with my car

You should use mine from the Haynes manual, those are very poorly set out. And don't have vital info like wire colour. If you do a lot of car work then you should buy the Haynes manual yourself, i paid around £22.