Ford EECV PCM - fiesta man

I have a 1.25 fiesta which I believe has a EECV PCM at its heart.

What I would like to acquire is a pin-out diagram for the ECU, as I have suspicions about my Lambda sensor, and want to try and establish if it is sending voltages to the ECU which are within the expected range - I have a lap-top I can use to log the values.

The reason I want to do this is the car occasionally (it had to be that way didn't it...) hesitates slightly around 4000rpm under WOT, which it hasn't done in the past. Having trawled through the 'net I've discovered people experiencing a similar issue, which eventually they traced to the Lambda sensor.

I don't fancy taking the car to Ford to have the car interogated for fault codes, as I simply don't have the time during the week, and I'm reluctant to spend money if they can't find a problem owing to the intermitent nature of the fault.

So basically could anyone point me in the right direction for a pin-out diagram, or maybe even suggest an alternative to taking the car to ford - i'd much rather hand the cash to smaller firm that might offer a degree of customer service!

All help appreciated,


Ford EECV PCM - Techmad

From my understanding, the Ford EECV interface is a serial communication interface. It requires a computer or scan tool to send requests for sensor values to the PCM. Unfortunately, it is not possible to just probe the port and get analogue sensor values, such as the Lambda sensor voltage that you mention.

If you are looking for an alternative to paying for a diagnostic code read at Fords, you can buy one of these:

This tool will communicate with Engine Management Systems (including Ford?s EECV) and display/clear any stored fault codes. It will not show real-time sensor values (you need to spend bigger money if you want to monitor these) but if an oxygen sensor fault code is present, it should display it.

Hope this helps,
Ford EECV PCM - fiesta man
cheers for that - i was aware of the OBDII port, but hadn't searched for any readers.

I was just hoping someone knew the pin connections on the in-bound side so i could probe the cable from the lambda and check the voltages - not too keen on trying to read the voltages at the other end!
Ford EECV PCM - Andrew Moorey (Tune-Up)
I'll dig out the pin data for you tomorrow but it is really easy to measure the voltage at the lambda sensor on this particular engine. Locate the sensor which is on top of the exhaust manifold and follow its wire for a few inches until you come to the loom connecting plug. Open up a paper clip and take the sharp edge off one end with a bit of emery and slide it into the plug down the BLACK sensor wire. Connect it to positive meter probe Start the engine and run it at a fast idle for a minute or so and the voltage should be seen to be fluctuating rapidly between .3 and.8v. It is better seen on a graphing meter or better still an oscilloscope set to .4v per div Y axis and a timebase of 1 second per div X axis. The sensor should cycle between max and min at, at least, 60Hz, any less and the sensor is getting 'tired' If it is really lazy you will actually hear the engine revs rise and fall as the sensor 'swings' between rich and lean.

Simplicate and add lightness!!
Ford EECV PCM - elekie&a/c doctor
I think you will find lambda signal at pin 60 of PCM ,but it is quite difficult to access.As suggested we use dedicated equipment to lift info thro OBD serial link ,much easier.
Ford EECV PCM - fiesta man
Thanks very much - i was wondering which wire was the one to connect to directly, but it isn't clear in the haynes manual.

Ford EECV PCM - fiesta man
Ok, an update...

I've tested the sensor on an oscilloscope, whilst holding the car at ~3000rpm. The signal generated by the sensor was switching between approx .3v and .9v, which is about right from what has been said above, but was switching at about 3hz. What I did notice on the main signal, was the that there were spikes superimposed, which were consistantly at 0.04s intervals, and in time with the signal i captured from another of the sensor wires.

Despite the sensor not outputting at 60hz, there was no appreciable rev wavering.

As a further comment, when the car is started, the engine revs will regularly rise to around 2k, and then for the first couple of second the car does seem to hunt for the idle point (circa 800rpm) at about 2hz, with the revs gradually dropping from 2k with each iteration.

Any ideas anyone?
Ford EECV PCM - Techmad

How many miles has the car done? If it has done over 70K then it is worth considering changing the Lambda sensor. Lambda sensors tend to degrade and provide a slower reaction to changing exhaust gas levels over time, as mentioned by Andrew Moorey above. You can buy universal oxygen sensors for around £35.

From my understanding, if the Engine Management System thinks the Lambda sensor has failed, it will ignore the values coming from the sensor and substitute them with a guess value. However, I believe this will normally put the car into Limp-Home mode. It is much more common for an oxygen sensor to provide lagged readings to the ECU causing the engine to use up more fuel run less smoothly.

Ford EECV PCM - pastyman
Get hold of Car Mechanics magazine and go to the back issues page and buy the Feb 98 issue, the engine diagnostics article for that month is the Ford EEC-V system. If not available, they can reprint the article for a couple of quid or so.
Hope this helps.



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