Cold weather P0171 (and P0174)

[wsryan]

Ok, so here’s my situation:
2004 TB EXT, 5.3 L
The last couple of winters, when the outside air is cold, would throw the P0171, but I never noticed any change in performance, and it would not throw a code on warm days, so I ignored it. This winter, about four times has gone into REP mode. After the first time, I cleaned the MAF sensor—would still throw the P0171 on cold mornings, but no REP for a couple of weeks, but then it recurred. So, I then changed the MAF sensor. Again, lots of the P0171, then after a few days, REP again a couple of times. I now pull over, turn it off and restart it and it is OK.

After the REP, I then get these readings:

P0171 Generic
1. Fuel Trim System Lean
2. Fuel Trim System Lean Bank 1

P0174 Generic
1. Fuel Trim System Lean Bank 2

P0220
1. Throttle Position (TP) Sensor 2 Circuit 2. Throttle Position (TP) Sensor 2 Circuit.


Anyone have the best guess as to how to proceed from here? I have the INNOVA 3130 ScanTool…

Thanks for any help you can provide.

 

[The_Roadie]

Welcome! Glad you found us.

Typically, lean codes like that don't trip the REP feature. The PCM saves that for disastrous issues like a throttle body sensor or wiring issue. I'd be looking at the wiring harness very well around the throttle body, and then swap the TB itself.

 

[wsryan]

Thanks! I will give it a try...but not tonight, since my daughter has it on the road...

I really appreciate the input!

 

[BRomanJr]

Ok, so here’s my situation:
2004 TB EXT, 5.3 L
The last couple of winters, when the outside air is cold, would throw the P0171, but I never noticed any change in performance, and it would not throw a code on warm days, so I ignored it. This winter, about four times has gone into REP mode. After the first time, I cleaned the MAF sensor—would still throw the P0171 on cold mornings, but no REP for a couple of weeks, but then it recurred. So, I then changed the MAF sensor. Again, lots of the P0171, then after a few days, REP again a couple of times. I now pull over, turn it off and restart it and it is OK.

After the REP, I then get these readings:

P0171 Generic
1. Fuel Trim System Lean
2. Fuel Trim System Lean Bank 1

P0174 Generic
1. Fuel Trim System Lean Bank 2

P0220
1. Throttle Position (TP) Sensor 2 Circuit 2. Throttle Position (TP) Sensor 2 Circuit.


Anyone have the best guess as to how to proceed from here? I have the INNOVA 3130 ScanTool…

Thanks for any help you can provide.

For the Lean codes, Have you watched the (2) Front O2 Sensor readings? If you are over 100k miles I would check that the sensors were still very active when warmed up.
I just changed my O2 sensors at 189k and it smoothed out the rough idle I was chasing but never threw a code.

As for the REP, I had a bout of REP events a year ago and the fix for mine was to clean and add dielectric grease on the connectors of the Throttle Controller located on the firewall wedged between the Brake Booster and the Driver side Fender. After the cleaning/grease no more REP events. I cleaned/greased the Throttle Body connector previous to this with no improvement.

 

[wsryan]

This is what I got on live data...this was after warmed up...And no DTC at the time. Maybe I should set my scanner to record live data when DTC is triggered. Would that help any?

I don't really have any idea what I am looking at here...

O2S B1 S1(V) 0.300 (.055-.870)
O2S B1 S2(V) 0.120

O2S B2 S1(V) 0.315 (.035 -.915)
O2S B2 S2(V) 0.165

I did check the harness to the throttle body, and cleaned it. No obvious problem there.

Which of the devices/harnesses between the brake booster and fender is the throttle controller?

 

[dcbenvoy]

For what it's worth, I get the same code ocassionally when the weather is cold.

It always goes away after I drive a while. I have a factory O2 sensor on eone side and an after market O2 sensor on the other side.

It is always the side with the aftermarket sensor that fails. I bought an ac delco sensor to replace it but since it's always cold when it happens I have trouble getting it done.

In light of Roadie's post I should switch sensors to rule them out because a TB sounds more serious and frankly, roadie has never steered me wrong.

 

[jake 03]

For what it worth,the earlier 5.3s have intake gaskets that are prone to failure and they always manifest themselves as p0171 and 174,and as they get worse,rough idle after a cold start. They are relatively cheap and easy to replace so I would start there.
As far as the REP and P0220, you need a throttle body. That code indicates a failure of the tp sensor and because it is internal you have to replace the whole tb.
Hope this helps and if you have any other questions feel free to ask.

 

[dcbenvoy]

Jake,

That makes a lot of sense. It only does it when it is super cold out.

I'm going to look into the intake gasket.

Thanks, Doug

Ryan, did you get it figured out?

 

[wsryan]

No, haven't figured it out yet. I did clean the throttle body connectors--haven't had any recurrence of the REP, but still have the really rough idle in cold weather, and it doesn't seem to improve any after the engine warms up. It only gets better if the weather gets warmer. Maybe I should just move to Florida?

On a somewhat (I think) unrelated point, I don't remember ever changing the sparkplugs. I have >170K miles...

 

[wsryan]

Welcome! Glad you found us.

Typically, lean codes like that don't trip the REP feature. The PCM saves that for disastrous issues like a throttle body sensor or wiring issue. I'd be looking at the wiring harness very well around the throttle body, and then swap the TB itself.

Well, I changed the throttle body. Still get lean codes and now more frequent REP, more commonly at highway speeds, it seems. The only different code I see now is P1516, Throttle Actuator Control Module Actuator Position Performance. (Is that the cause or the effect of the REP?)



On another thread, I found this comment: "Recommend that while you are replacing the TB to disconnect the battery for 30 minutes to reset the PCM. We usually do this while cleaning the TB. Might be a good idea so it resets itself to the new TB and TPS."

Is that something I should have done, and is that likely to be the source of my problem?