Electrical issues or PO171 PO174 ???

My brothers 07 Chevy 1/2 ton LT Texas Edition 4.8 has given these two codes in the past but the CEL does not stay on constantly.
PO171 System to lean (bank 1)
PO174 System to lean (bank 2)
Only thing is not at the same time. Once it was PO171 the next time PO174.
We've disconnected the MAF sensor and it made no difference. We cleaned the MAF and no difference so I think its a short.

Odd thing is it has not shown up in a while but when this started it was kinda hard to start. You could turn the key and it acted like there was no fuel and then it would turn over again and it would come close but not start and then it would start.

Another odd thing is sometimes the windows won't work right either. Back window may go down but not up or the front may go down but you could wait and it would go up and if you walk around to the back door and hit the switch the back window goes up. He even had the speaker in the passenger door stop working so he replaced it. Now it stopped working again.

My opinion is there's an electrical problem with the Ignition Switch or a short somewhere else.


Please any help is appreciated

[j cAT]

Originally Posted by dksram

My brothers 07 Chevy 1/2 ton LT Texas Edition 4.8 has given these two codes in the past but the CEL does not stay on constantly.
PO171 System to lean (bank 1)
PO174 System to lean (bank 2)
Only thing is not at the same time. Once it was PO171 the next time PO174.
We've disconnected the MAF sensor and it made no difference. We cleaned the MAF and no difference so I think its a short.

Odd thing is it has not shown up in a while but when this started it was kinda hard to start. You could turn the key and it acted like there was no fuel and then it would turn over again and it would come close but not start and then it would start.

Another odd thing is sometimes the windows won't work right either. Back window may go down but not up or the front may go down but you could wait and it would go up and if you walk around to the back door and hit the switch the back window goes up. He even had the speaker in the passenger door stop working so he replaced it. Now it stopped working again.

My opinion is there's an electrical problem with the Ignition Switch or a short somewhere else.


Please any help is appreciated

first thing to do is measure fuel pressure and do the fuel pressure test. then if this is correct /also drive vehicle when checking pressures. next would be vacuum leaks and any crankcase oil fill/dip stick/hoses being correct. check the after MAF ducting for proper connection and no leaks. on earlier models the pcv/hose would be also checked.

short circuit would blow fuse.

if an electrical problem were there it would be power/ground electrical circuits/components for fuel pump.

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