02 sensor Issues

[ShiftedReality90]

Greetings

This is my first post on this site so go easy on me I obtained my first Puma a month ago (adore the car) and am wondering if I could obtain some help?

My car has been having issues with MPG and fuel usage since buyng it. The car literally drinks petrol like it's on a night out in town. Just drinks it and drinks it. I am getting about 26MPG so I looked into the matter. I have plugged my OBD scan tool into the car and 2 codes were found.

P0136 and P0141 Now both are related to 02 sensor bank 1 sensor 2 so I figured I'd have a poke around and see if I could find a solution however I cannot find any sort of sensor in the engine bay. I have seen other posts and their cars have 2 02 sensors and the wires are located near one another (one blue and one green connector) on the firewall but my car has only sensor (gray connection) and that goes into the top of the manifold so I am baffled. I have a 1999 1.7L VCT engine.(V969 EDC) I have changed the spark plugs, air filter, oil and filter, coolant and fuel filter. All tyres are at Ford's recommended PSI. I'm just wondering why my OBD scan tool is picking up these codes if my car only uses 1 sensor? I have seen on another post that pre 2000 Puma's use 1 sensor and Post Puma's use 2. Mine being 1999 I imagined it would class as pre 2000?

Another issue but it might not be related is the Temperature gauge needle doesn't move from cold. It gets power as it moves from it's resting position when I turn ingnition on. It stays at cold throughout my journey despite the engine running at normal temperature. OBD live data states the car is at 86-87 degrees when driving. Could a previous owner had messed about with the ECU and messed it up?

I would appreciate any help as I want these issues sorted as soon as possible.

Thanks

 

[hotrodspike]

Hi mate

Have you looked if there's a thermostat fitted? A previous owner might have taken it out because of overheating problems. If you have got one in, change it anyway, it might have failed in the open position, letting the coolant through the rad all of the time.

Have you checked for the other O2 sensor on the cat as that is Sensor 2, Sensor 1 is the one on the manifold, your car might be one of the "changeover" models inbetween series 1 and 2 so could have bits from the early and late models.

When you change the sensor, don't fit a "Universal" sensor, they're useless!

 

[CherryVimto]

According to what I have found, code:

P0141 relates to a problem with the heating element in the O2 sensor.
https://www.autocodes.com/p0141_ford.html
P0136 relates to the O2 sensor voltage readings being out of range for an extended period
https://www.autocodes.com/p0136_ford.html

Code P0141 may have possibly caused the ECU to throw the P0136 code.

So, based on the info above I would find and check the fuse for the O2 sensor, check to see if it is actually plugged in correctly and there is no obvious damage to any of the associated wiring.
After that, I personally would probably look at replacing the sensor.

Even if the thermostat was missing/stuck open the temp gauge SHOULD still register the coolant temp. The only issue that would arise would be it will take longer for the coolant to reach operating temp and even longer still if there is road movement. As mentioned above it would be worth checking/replacing it anyway.
I would suggest that either the gauge itself is faulty or the sensor/sender that detects the coolant temp may be faulty or disconnected. See if there is a fuse for that circuit and check that.

 

[Ian G]

This has all the hallmarks of the ECU being changed.

 

[CherryVimto]

[post]366725[/post] This has all the hallmarks of the ECU being changed.

What makes you say that Ian? Whats your line of thought..?

Edit: car was single O2 sensor ECU and been swapped to a twin O2 sensor ECU but throws a code due to there now being one O2 sensor 'missing'? Also hence why the temp gauge fails to work (wrong pin-out on ECU)?

 

[ShiftedReality90]

[post]366725[/post] This has all the hallmarks of the ECU being changed.

Firstly, thank you all for your amazing responses. Secondly, Ian G you have taken a thought out of my mind. I am suspecting that this is the case as evidence points towards it. How can I check to confirm this suspicion? As I said in my first post, the OBD scan tool picks up a 2nd 02 sensor issue but I can't find any location of it. I'll attach some pictures to show what I mean.

Pete

 

[ShiftedReality90]

 

[ShiftedReality90]

 

[ShiftedReality90]

 

[DOH]

With Regard to the heavy fuel consumption issue, Replace the Lambda(o2) Sensor with a new one, your fault code reader confirms that its faulty.
You will need a 22mm ring spanner with a dogleg or the correct lambda removal socket and undo the 2 bolts on the exhaust manifold heatshield nearest the bulkhead and bend out of the way.
Avoid removing the other heat shield bolts, as they rust badly into the exhaust manifold and some will shear off !

Use either a NTK(made by NGK) or a Bosch sensor , that is specifically listed for the 1.7 Puma. They are approx £70.

In addition check the fuel pipes that are hidden by the heat shield along the centre of the car (in particular under the handbrake /gearstick area), they can corrode badly and not be spotted by the MOT tester.
Other common places are leaks at the fitting of the fuel filter

 

[CherryVimto]

To confirm whether the ECU may have been replaced or not, you may need to remove it to see which one it is.

Disconnect the battery.
Passenger footwell by the door there should be a cover hiding the OBD socket. Behind that piece of carpet is the ECU tucked up beside the dash. It is held in with a black metal cover which (as standard) should be held in with 2x rivets. If they are still there you will need to drill the rivets out. You can then slide the ECU down. I'm not sure if you can see the ECU 'name' or whether it is on the other side so you may need to undo the big plug from the ECU and pull the whole thing out.

If Ians suspicion is correct about the ECU being swapped then I doubt there will be two rivets holding it in... unless someone was very conscientious and put it back together properly!

 

[ShiftedReality90]

[post]366750[/post] To confirm whether the ECU may have been replaced or not, you may need to remove it to see which one it is.


Disconnect the battery.
Passenger footwell by the door there should be a cover hiding the OBD socket. Behind that piece of carpet is the ECU tucked up beside the dash. It is held in with a black metal cover which (as standard) should be held in with 2x rivets. If they are still there you will need to drill the rivets out. You can then slide the ECU down. I'm not sure if you can see the ECU 'name' or whether it is on the other side so you may need to undo the big plug from the ECU and pull the whole thing out.

If Ians suspicion is correct about the ECU being swapped then I doubt there will be two rivets holding it in... unless someone was very conscientious and put it back together properly!

View attachment 1

 

[Ian G]

Those bolts are non-standard.

I say its been changed because your car is only wired for one lambda sensor but the ECU is complaining of not seeing the signal from the second. Hence an early ECU would not complain of the missing signal.

In addition the later ECU supplies the temp signal to the dash on a different pin.

Those two facts together, and your third with the picture of those bolts is fairly conclusive.

Ironically this will probably mean that when you change to the correct ECU (or move the temp signal pin and ignore the fault code) that your fuel consumption will be unchanged.

Not entirely sure but my understanding is that the second sensor only has a limited role in measuring cat efficiency and is not used in fuel metering calcs although that is only an assumption. It may be that it also has a role in offering some redundancy to the metering job that the first sensor is doing.

That said you also have a different first sensor being that you should have the green round plug type on the different loom to match that later ECU. Whether that makes a difference who knows, they are definitely different part numbers due to the plug being incompatible with the early loom but whether your early lambda would cause fuel problems in the later ECU, no idea. Also not important if you intend to put the correct one back in.