ECT Rear change sets PO125?

P0125 Engine Coolant Temperature (ECT) Insufficient for Closed Loop Fuel Control

A buddy and I are tuning a '14 Charger. We set the ECT Rear up to 374* to take the rear O2's out of the picture in closed loop and after a while it tripped the PO125 DTC. It seems to make sense but I have the same setting on my '13 Challenger RT, as do others, and I've never thrown this code.

I'm aware of this code being reported on several stock vehicles but this just started after his tune so I suspect it's related to the ECT Rear. Has anyone else experienced this?

What thermostat is he running?

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Originally Posted by ElecTech

What thermostat is he running?

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Stock right now. I was going to set his ECT Rear back to stock settings first, and if the code persists, have him drop to a 180*.

So here is an interesting follow up.

1. My buddy was getting some surging after his tune. He remembered that he had increased the throttle boost by 15% so he plugged in his Diablo and removed the throttle boost. The P0125 and his surging went away. I attributed this to possibly messing with the TCC apply/release.

2. He unmarried his Diablo, taking him back to stock and sold it.

3. He added a 180* tstat. No surging and no codes.

4. I rewrote his tune and his surging and P0125 code came back. Now, I get the surging part. I made his Electronic Throttle tables match that of a stock Charger and that went away but the P0125 code is also back and I cannot fathom how that code has anything to do with throttle %. I believe that you should be able to extend his ECT / Closed loop time delay to resolve this.

Has anyone else run into anything similar? The tstat is known good and coolant levels are good. I noticed that Closed Loop Enable | Enable Delay is 2 seconds shorter on the Charger vs. the Challenger so I'm going to bump his up by 2 sec. We have the same model 180* tstat and I see on Lx Forums that this code is pretty common.

The exact set times for that code (which you prob saw) is below, did you modify his fan settings? This code doesn't have anything to do with the rear 02s, its basically telling you that from the time you start the car until it hits the Closed Loop Enable temp is too long. What temp do you have in the Closed Loop Enable temp?

P0125-INSUFFICIENT COOLANT TEMP FOR CLOSED-LOOP FUEL CONTROL

When Monitored: With battery voltage greater than 10.4 volts and after engine is started.
Set Condition: The engine temperature does not enable closed loop. Failure time depends on start-up coolant temperature and ambient temperature. (i.e. 2 minutes for a start temp of 10�C (50�F) or up to 10 minutes for a vehicle with a start-up temp of -28�C (19�F). Two Trip Fault. Three good trips to turn off the MIL.Possible Causes
LOW COOLANT LEVEL
THERMOSTAT <<< most likely cause
ECT SENSOR

I am inclined to agree with Pector55's theory. I also get the P0125 code. My ECT Rear temp is set to 374. My Coolant Temp for Closed Loop enable is set to the factory 5 degrees F. There is a Enable Delay Rear table which states: [ECM] 34454 - Closed Loop Enable Time Rear: ECT must be above Closed Loop Enable Temp Rear for this amount of time to enable closed loop fuel for Rear O2. Unless the delay can be set to zero, the conditions will never be met.

Try setting rear temp back to stock and use the dtc switches to kill the O2 codes ;)

Well, it definitely doesn't like zero for the values.

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Originally Posted by RunNE1

I am inclined to agree with Pector55's theory. I also get the P0125 code. My ECT Rear temp is set to 374. My Coolant Temp for Closed Loop enable is set to the factory 5 degrees F. There is a Enable Delay Rear table which states: [ECM] 34454 - Closed Loop Enable Time Rear: ECT must be above Closed Loop Enable Temp Rear for this amount of time to enable closed loop fuel for Rear O2. Unless the delay can be set to zero, the conditions will never be met.

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You are not interpreting the code its throwing correctly, the test is set by you in the delay table both for the front and rear sensors closed loop, the PCM is going to monitor based on your delay time since startup if the coolant was above the temp set in your Closed Loop Enable (not rear but front). Setting your delay to zero means the PCM will say "after zero seconds the engine coolant temp must be above 5 degrees F or set the engine light." That's good for the fronts, but you have the rears set to a temp itll never reach.

Certain model years have the DTC monitoring for the rear sensors disabled, some have it enabled. Some model years have no rear 02 sensor fueling monitoring AT ALL, but itll still run the DTC test.

Best bet, set both front and rear enable temps and delay to stock, disable the MIL and SES lights for P0420, 0421, 0430, 0431.

Yes, I realized my mistake. And max delay is 693 seconds, which is great if all your trips are 11 minutes or less. What happens if I enable rear fuel trims?

I had this same code after swapping in a 180 tstat and going catless. Recommendation to me was to set >Min Airflow Rear higher. Worked great.

However, this past Friday my Jeep was at dealer to get interior trim pieces replaced. Though I told them numerous times I did not want the ECM updates, and even signed and initialed for them not to install them, they did so anyways. Even matching to the original factory tune, they had made quite a few changes. But, now I set the ECT Rear to 374 and am not getting the p0125 code. Though I can't see a change in the update that would have an effect on this. So, back to things we can't see I suppose.

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Originally Posted by ElecTech

What thermostat is he running?

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I have this P0125 with a challenger currently, but I did disable the ECT rear's too. Running a 180 stat but this is the only dodge/jeep out of 3 with the same thermostat that has done this. Gonna re enable the rear O2 ECT and see if it goes away.

disabling the p0125 seems to leave it there but its kind of funky to get the light off being a "permanent code". I have had it off with the heaters also disabled in codes I also seem to remember having to clear it with the engine not running. the code stays with light off until a few tests from cold start ups run but never comes back until a rewrite. I am currently trying to keep all the trouble codes enabled minus the p0125 with just the rear 02s disabled and everything else stock settings. It was also off with all the rear 02 dtcs disabled.

Ok Im resurrecting this...Mine has beem on since I did the CAT delete... Whats the general consenus to get rid of this without just turning the MIL off?

Don't believe this can be prevented (without disabling DTC) if running a 180F thermostat, which is why it is recommended that folks in the northern states run 190-195F thermostats. I have increased the temps on the rear O2s and have never seen a P0125 pop up but I run a 195F thermostat.
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