[RM2488]

Hey guys
Having a bit of an issue on my petrol Fiesta. It went into limp mode recently (with a light). So I took out my OBD2 scanner and it pointed to the O2 sensor. I duly checked the sensor with a multimeter and indeed the heater was gone. After all the horrible experiences I have had at ford A.S.C over the years, I chose to replace it myself. Now I have a check engine light again- P2100. It points to the throttle body... I removed it and cleaned it. Disconnected the battery for ECU reset. Verified all the connector contacts. Cleaned the MAP sensor. Verified that the new O2 sensor is working. The issue still crops up.

I have full throttle available until the car warms up (so the motor on the throttle body is fine). After that, it goes into limp mode with the same P2100 error code. But ONLY if the car is in gear and in motion. It DOES NOT enter limp mode until I actually get moving. Any clues on how to fix it?
P.S. If anyone has a Fiesta and a scan tool, what are the readings you get for the MAP sensor?

[hserus]

You had better get this done at a good ASC. Find another if the one you normally use doesn't work for you. They've improved their service standards over the years by the way.

[akshay380]

Originally Posted by RM2488

Hey guys
Having a bit of an issue on my petrol Fiesta. It went into limp mode recently (with a light). So I took out my OBD2 scanner and it pointed to the O2 sensor. I duly checked the sensor with a multimeter and indeed the heater was gone. After all the horrible experiences I have had at ford A.S.C over the years, I chose to replace it myself. Now I have a check engine light again- P2100. It points to the throttle body... I removed it and cleaned it. Disconnected the battery for ECU reset. Verified all the connector contacts. Cleaned the MAP sensor. Verified that the new O2 sensor is working. The issue still crops up.

I have full throttle available until the car warms up (so the motor on the throttle body is fine). After that, it goes into limp mode with the same P2100 error code. But ONLY if the car is in gear and in motion. It DOES NOT enter limp mode until I actually get moving. Any clues on how to fix it?
P.S. If anyone has a Fiesta and a scan tool, what are the readings you get for the MAP sensor?

Hi I will post my readings tomorrow. Mine is 2009 1.6.

[Rohit_Quad]

Originally Posted by RM2488

I have full throttle available until the car warms up (so the motor on the throttle body is fine). After that, it goes into limp mode with the same P2100 error code. But ONLY if the car is in gear and in motion. It DOES NOT enter limp mode until I actually get moving. Any clues on how to fix it?

Ok, i know what you are talking about. This very thing happened to me for the first time, when i did a non stop Hyderabad to Bangalore run, with ambient temps around the 40 degrees mark. No signs what so ever all the way, but when i entered Bangalore and hit traffic, the car showed the exact signs you mentioned. I called up my guys in Hyderabad Ford, he said it was some sensor near the gear box that would have gone kaput temporarily. Said it could be that the gear box was over heating (extended use, without breaks at high speeds), so it would have really saved the car by putting it into limp home mode or, the sensor has become weak over time. Since i known him since long, he gave me 2 options.

1. He would arrange for a part in the Bangalore Ford ASC by the next working, don't remember the cost, but he said it was a half an hour job.
2. Wait for 15~30 mins, for the car to cool down, and be on my way.

I chose the second option, as it was a road trip to Coorg. This was almost 3 years ago, Feb 2016. Since then the issue repeated only once again, this summer, in April. 40+ degrees again, car was parked in the sun for more than 3 hrs (12pm !!), got in and drove for 30 minutes in traffic, same issue. But both times (2016 & 2018), thank god, i was just minutes away from parking the car in a covered parking lot, and go do my things (which did take more than a couple of hours, both times). When i got back and started, all was well. Hence ignored it since i know what to do, when that issue occurs. I could have got it replaced, but since i couldn't replicate the problem at the SVC, nor could i get the car to behave like that again, when ever i want to test it (to check, if i replace the part), i just let it be. I do drive the car extensively on hot days, long distance drives, but it seems to occur only on some very certain conditions.

Hope this helps identify the problem. P.S. i drive a 2006 Fiesta, 1.4 Petrol EXI (1.14 Lakh Kms on the Odo now)

[interc00led]

Originally Posted by RM2488

Hey guys
Having a bit of an issue on my petrol Fiesta. It went into limp mode recently (with a light). So I took out my OBD2 scanner and it pointed to the O2 sensor. I duly checked the sensor with a multimeter and indeed the heater was gone. After all the horrible experiences I have had at ford A.S.C over the years, I chose to replace it myself. Now I have a check engine light again- P2100. It points to the throttle body... I removed it and cleaned it. Disconnected the battery for ECU reset. Verified all the connector contacts. Cleaned the MAP sensor. Verified that the new O2 sensor is working. The issue still crops up.

Are you sure that you got the correct replacement oxygen sensor ? Is it a ford OEM spare ?

If the oxygen sensor reading or TPS values don't fall within the expected limits, the ECU will go into limp mode.
Just disconnect the o2 sensor's electrical coupler and check if the P2100 code goes away after clearing it via obd scanner.

PS - the reason for having full throttle available until warm-up is because the ecu runs open loop till the o2 reaches it's operating temperature.

[RM2488]

@HSERUS- I would, if that were an option. But the ridiculous work done by both of the Ford ASC I have visited, multiple times, has killed my desire to own a Ford vehicle. Thinking of a Vento for my next ride.

@Akshay- That would be quite useful. I think the reading of 8 to 9 inches on the MAP is a bit suspect.

@Rohit- My issue crops up within 5 minutes, and it's winter here. Probably a different cause.

@intercooled- The replacement is a genuine, brand new sensor. I feel like the old sensor might have been sluggish and masking another issue. The car does enter closed loop. Throws up an issue when I slot in a gear and start moving. That too if I rev past 2k. I can rev it to the limit in neutral, even after the car is at operating temp. Disconnecting it stops the P2100 code from showing up- It complains about the O2 sensor only then.

[dhanushs]

@RM2488 - I’m not sure how to solve the problem, but if you are stuck on road with a faulty O2 sensor, you can just disconnect the plug to the sensor and run. The car might run rich.

[RM2488]

@dhanushs- Disconnecting the O2 gives P0030, but does not cause P2100 to recur. Unfortunately, P0030 also causes a limp mode.

[hserus]

Originally Posted by RM2488

@dhanushs- Disconnecting the O2 gives P0030, but does not cause P2100 to recur. Unfortunately, P0030 also causes a limp mode.

Throttle Actuator Control Motor Circuit Open (TACM) - P2100
Heated Oxygen Sensor is P0030 - which is quite likely when you disconnect O2

P2100 could be wiring faults, a dirty throttle body or calibration required.

[Jaggu]

Was the car running fine (in motion) after you replaced the O2 sensor? Or this happened as soon as you replaced the O2 sensor and tried moving the car.

Details of error code and trouble shooting is given in the following link. https://www.obd-codes.com/p2100

Ford do have reliable workshops now, do check with fellow members if they can refer to a known one for this job. Should be fairly straight forward job.

[Rohit_Quad]

Originally Posted by RM2488

@dhanushs- Disconnecting the O2 gives P0030, but does not cause P2100 to recur. Unfortunately, P0030 also causes a limp mode.

I think you should check all the wiring to and from the throttle body and also check if all the fuses are ok.

[RM2488]

Originally Posted by Rohit_Quad

I think you should check all the wiring to and from the throttle body and also check if all the fuses are ok.

Already done. No issues found. Also checked the throttle plate position range- 1k resistance at closed, 2.2k at wide open, and smooth all the way through.

[Jeroen]

Originally Posted by RM2488

Already done. No issues found. Also checked the throttle plate position range- 1k resistance at closed, 2.2k at wide open, and smooth all the way through.

It the control motor and or its circuit, not the position sensor.

Next, try and check the signal from the ECU to the actuator control motor. If you have access to an OBD scanner/analyser with live data feed you might be able to see the signal on the OBD analyser.

I had a similar problem on my car:

https://www.team-bhp.com/forum/diy-d...ml#post4469547

Looks like you have done a thorough visual inspection of all electrical wires already. I recently had several electrical issues on two of my cars, both due to poor connection in a connector. Do the connectors fit tightly. Mechanically, but also do the little contracts inside the connectors fit properly. Sometimes they break or become loose. Verify the various wires are solidly attached to the various connectors, give a gentle good tug at each wire.

Good luck!

Jeroen

[RM2488]

I am 99% sure I have fixed the issue. Surprisingly, it appears to be a failing battery- 12.2V before engine start. No MIL since I replenished fluid and gave it a charge.

[a4anurag]

Originally Posted by RM2488

I am 99% sure I have fixed the issue. Surprisingly, it appears to be a failing battery- 12.2V before engine start. No MIL since I replenished fluid and gave it a charge.

What is the voltage that you observe during cranking? Is it going below 10V?