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Discussion Starter #1
I ran some E-85 today and the Commander threw-up. It shows P1128 and P1129. Online sources show this as a TSB for using 35-40% Ethanol. The Commander had some regular unleaded in it when I filled it. Anyhow, can I shut this off myself? The Commander is out of warranty and I don't want to pay for a reflash if I can avoid it.
 

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I ran some E-85 today and the Commander threw-up. It shows P1128 and P1129. Online sources show this as a TSB for using 35-40% Ethanol. The Commander had some regular unleaded in it when I filled it. Anyhow, can I shut this off myself? The Commander is out of warranty and I don't want to pay for a reflash if I can avoid it.
What year and does your Commander have flex fuel capability?
(Meaning, is it a E-85 4.7 V-8?)

Rob
 

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P1128 - CLOSED LOOP FUELING NOT ACHIEVED - BANK 1
P1129 - CLOSED LOOP FUELING NOT ACHIEVED - BANK 2


When Monitored:
Engine running in closed loop mode.

Set Condition:
Enable conditions are met and the 02 sensor has not been in closed loop control at least once on each of the two consecutive trips, the MIL illuminates and the DTC is set. Two Trip Fault. Three good trips to turn off the MIL


Possible Causes

  • RESTRICTED FUEL SUPPLY LINE
  • FUEL PUMP INLET STRAINER PLUGGED
  • FUEL PUMP MODULE
  • O2 SIGNAL CIRCUIT
  • O2 RETURN CIRCUIT
  • O2 SENSOR HEATER OPERATION
  • O2 SENSOR
  • MAP SENSOR OPERATION
  • ECT SENSOR OPERATION
  • ENGINE MECHANICAL PROBLEM
  • FUEL FILTER/PRESSURE REGULATOR (HIGH)
  • PCM
 

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Discussion Starter #4
The Commander is an '07 with the 4.7 flex. These are not generic codes. Chrysler has a TSB for a problem with ethanol use. I'm just wondering if I can turn off the check engine light myself.
 

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Discussion Starter #7
I was hoping that removing a battery cable would reset it. I will need to wait until I run the E-85 out so the light doesn't come back on. Everything seems to work except the factory remote start. It starts and runs for about 5 seconds and shuts off. I'm thinking it won't let you run the vehicle with a DTC code in place.
 

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Discussion Starter #9
I put some non E-85 in the XK today and ran a few errands. The check engine light went off and the remote start is now working again. I'll have to see if it stays off but, for now everything is back to normal.
 

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Dtc P1128 and P1129

Just got this code yesterday. I've read through this thread and was wondering if anyone has had this since, and what was the culprit? And what does "engine running in closed loop" mean? Also, I never run less than 87 oct and have the 3.7L
 

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A bad idle air control (IAC) valve could throw this code. After some trouble shooting and help from the counter guy at Autozone, I decided to by a new one for $66. Easy to install, remove the air plenum, and one screw holds the IAC into the throttle body, right side. Definately an improvement in response time. I'll clear the code and see what happens.
 

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Still have the codes even after replacing the IAC. After reading on jeep forum, i'm thinking the bosch ox sensors installed 2yrs ago are the culprit, read that NTK ox sensors are oem and have lower set/opening points. will try this and post later.
 

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Keep us updated.
 

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I ended up buying the OEM oxygen sensors from Mopar.com , the exact ones the 3.7 calls for. Both of them are before the cat., not too difficult to acess, if you have the proper socket, which i borrowed from Advance. After install, reset computer and have not seen the dtc since, about 2 weeks now. If you do need to replace you Ox sensors, DO NOT USE BOSCH. GO TO DEALERSHIP, OR MOPAR ONLINE.
 

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Thanks for the update ! :thumbsup:
 

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No prob. Glad to figure this one out.
 
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