P1128, P1129 07 Dodge Ram 5.7L

[curtjames37]

The CEL came on in my truck a few days ago. I did the key on-off trick and pulled these two codes:

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

Sometimes it will take 5-6 seconds of cranking for the truck to start. It happens pretty rarely. Also, driving home from work this morning there was a slight hesitation taking off from a stop sign. That is the first time I experienced that symptom. Otherwise, the truck runs fine.

There doesn't seem to be a whole lot of information on this on the internet. From what I could find the possible culprits are the MAP sensor, the 02 sensors, and a fuel delivery/pressure problem. I will check the fuel pressure first thing in the morning.

Any other ideas? It seems unlikely that both upstream 02 sensors would fail at exactly the same time. That would seem to point to the MAP given the fuel pressure checks out? I hate to start throwing parts at it.

Thanks in advance for the help!

 

[The_Eric]

We're going to need more info - at minimum, what year is it and how many miles are there on it?

 

[curtjames37]

Originally Posted By: The_Eric
We're going to need more info - at minimum, what year is it and how many miles are there on it?


It's a 2007 Dodge Ram 5.7L. Just rolled over 50,000 miles.

 

[The_Eric]

Do you have a scanner that reads live data?

A few things that will prevent closed loop operation and/or hard starting/hesitation are:

Low coolant temp via bad t-stat/defective sensor
Defective O2 sensor heater circuit(s)
Defective O2 sensor(s)
MAP
Air temp sensor

Check your air filter and do the fuel system test too.

 

[curtjames37]

Originally Posted By: The_Eric
Do you have a scanner that reads live data?

A few things that will prevent closed loop operation and/or hard starting/hesitation are:

Low coolant temp via bad t-stat/defective sensor
Defective O2 sensor heater circuit(s)
Defective O2 sensor(s)
MAP
Air temp sensor

Check your air filter and do the fuel system test too.


Just finished checking the fuel pressure. It was around 58 PSI at idle +/- a few PSI. From what I have found that seems to be within spec. The air filter has less than 5000 miles on it but I pulled it and inspected it anyway. It still looks to be in good condition. I checked the temp at the thermostat outlet with an IR temp gun and it was around 200 degrees after a 5 mile drive. Unfortunately, I do not have a scanner that will read live data.

Thanks for the help.