Fiat Punto 1.2 1996. non start, no rpm signal from ecu

[Dave Williams]

Hi guys

got the above vehicle, which will not start, scanned it & got

P002B ECU Defect (ROM)
P002E Engine speed sensor circuit

in live data there is no RPM

scoped crank sensor got good trace, but replaced it anyway

ckecked all feeds & earths to ECU all good

replaced ECU with refurbished unit from Autotec in poole, still no start & P002E Engine speed sensor circuit fault logging

there is no immo on this one

any help appreciated
Dave Williams
Swiss Road Garage

[kurt]

hi dave

Did you scope crank sensor at ecu to confirm wiring integrity

       kurt

[Dave Williams]

hi kurt

yes I did chek at ecu end

Dave Williams
Swiss Road Garage

[beachlife]

The contacts can be bad at the ecu on these.If you can try to tighten the ecu plug.

I have had a couple of puntos do this and most of the time it was just at the ecu plug, a bad contact.

[sparki1]

Hi. Was the sensor scoped under load or with ecu disconnected?
  Sparki.

[Doc...]

Hi Dave,

Out of interest could you put the captures up in the scope section?

The more captures the merrier in the waveform library.

I personally like to scope at sensor and ECU where possible, it highlights any imperfections in the wiring / connectors.

Is the ECU an exact match for the original i.e. the pin config and voltages / grounds identical?

Do you have wiring diagrams / pinouts for the system?

Cheers

Steve...

[Dave Williams]

Hi Guys

Thanks for replies

Beachlife, I have tried connections all spotless & tight also re-tweaked just to be sure

Sparkyi1, yes it was scoped at ECU with ECU connected, 10v switch perfect pattern.

Doc..., I will try & get some images of the trace, I use a Modis for scoping & I do not normally save them but I will have a go & post them

The refurbished ECU is the same part number & all pin configurations look the same, I was told by Autotec that it was a new board with my original software uploaded to the new one, They are going to send me a completely new unit Tuesday but I am not holding out hope it will work.

Yes I do have wiring diagram / pinouts from AD which match colour wise & pin position, I have retested all grounds & power which comes from the engine control relay which is all working fine, It cuts in & powers what it should at IGN on but when cranking does not stay locked in because of no RPM signal in ECU.

Dave Williams
Swiss Road Garage

[RobOneStop]

as stated
poor connections to ecu 
get some one to crank as you do a wiggle test on connections going into ecu
are you getting spark and injector pulse 
ive had a lot of trouble with the coil wires from ecu
gentle wiggle whilst being cranked normaly fires them into life 

[Doc...]

Hi Dave,

Thanks for that,

Modis is a 4 channel yes? Scoping at the ECU and sensor whilst doing the wiggle test may reveal an anomaly.

I had a P38 not long ago that wouldn't start, different system I know but it was losing an ECU earth when cranked, this was found with a bit of lateral thinking and to be honest, blind luck.

I would be tempted to look at each sensor / component / cicuit in turn that shares any feed or earth with the CKP.

HTH

Doc...

[Dave Williams]

Hi Guys

Still got this vehicle

Found out now that there is an immo on it, but there is no light or key to indicate if it is accepting the key coding

If it was immobilised would I still be able to read ECU or would it block it from showing live data.

Dave Williams
Swiss Road Garage