Codes P0174 & P0171. Dealership is lost
#1
5th Gear
Thread Starter
Codes P0174 & P0171. Dealership is lost
I have a 2010 Rx350 that throws the codes 0171 & 0174 intermittently. The check engine light will come on along with the traction control light. Weird thing is the check engine and traction control light will periodically go off by itself without me clearing the codes. I took it to the dealership explained the issue and left it for 8 days. They went through all the testing that is required for those codes and found absolutely nothing. They replaced all gaskets related to the possible problem, did a smoke test and plenty of other diagnostic tests, they basically got to the point to where they were ordering parts and replacing then taking them off and returning them because nothing was fixing the issue. So I finally just picked it up because I was going on vacation and didn’t want it to stay there for two more weeks. Has anyone had this problem that they found a solution for?
#2
Moderator
You are very lucky as they are accepting a return after installing part(s).
Lexus dealerships have trained mechanics and they have a regional expert who can be looped in to consult. I would say talk to the service manager.
If you are diagnosing by yourself, try reading live data. Some savvy member may be able to give you guidance.
Salim
Lexus dealerships have trained mechanics and they have a regional expert who can be looped in to consult. I would say talk to the service manager.
If you are diagnosing by yourself, try reading live data. Some savvy member may be able to give you guidance.
Salim
#3
Intermediate
I have a 2010 Rx350 that throws the codes 0171 & 0174 intermittently. The check engine light will come on along with the traction control light. Weird thing is the check engine and traction control light will periodically go off by itself without me clearing the codes. I took it to the dealership explained the issue and left it for 8 days. They went through all the testing that is required for those codes and found absolutely nothing. They replaced all gaskets related to the possible problem, did a smoke test and plenty of other diagnostic tests, they basically got to the point to where they were ordering parts and replacing then taking them off and returning them because nothing was fixing the issue. So I finally just picked it up because I was going on vacation and didn’t want it to stay there for two more weeks. Has anyone had this problem that they found a solution for?
Personally I would check the intake manifold seals if nothing else solve the problem since a bad intake seal can allow un-metered air to enter the manifold pass the sensors and mess up the air/fuel ratio the ECU is measuring which can trigger the warning for both banks like in your case.
#5
5th Gear
Thread Starter
#6
5th Gear
Thread Starter
Just a guess, but maybe an air/fuel ratio sensor is bad. I believe that bad air/fuel ratio sensors can trigger the two codes as well, however it is odd that both banks are bad at the same time. I would also check the wiring harness ground connections for any bad connections.
Personally I would check the intake manifold seals if nothing else solve the problem since a bad intake seal can allow un-metered air to enter the manifold pass the sensors and mess up the air/fuel ratio the ECU is measuring which can trigger the warning for both banks like in your case.
Personally I would check the intake manifold seals if nothing else solve the problem since a bad intake seal can allow un-metered air to enter the manifold pass the sensors and mess up the air/fuel ratio the ECU is measuring which can trigger the warning for both banks like in your case.
#7
Intermediate
My next best guess is may be a bad ground connection(lose or broken wire) on the chassis.
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LaytonSparks (02-24-24)
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#8
Moderator
Salim
#9
Your long term fuel trim is pretty high, the link below might be helpful for you.
https://www.clublexus.com/forums/rx-...4-codes-3.html
https://www.clublexus.com/forums/rx-...4-codes-3.html
#10
5th Gear
Thread Starter
Your long term fuel trim is pretty high, the link below might be helpful for you.
https://www.clublexus.com/forums/rx-...4-codes-3.html
https://www.clublexus.com/forums/rx-...4-codes-3.html
I appreciate the help!
#11
Instructor
Assuming the dealership ran the smoke test correctly, and ruled out a leak in one of the several vacuum hoses, have they looked at the MAF? Is there a CAI installed by any chance or a nonstandard air intake setup? The MAF is a PITA to change out because the windshield cowl has to come off, just like when replacing the intake manifold, so curious if they switched out or tested the MAF while the cowl was off.
#12
5th Gear
Thread Starter
Assuming the dealership ran the smoke test correctly, and ruled out a leak in one of the several vacuum hoses, have they looked at the MAF? Is there a CAI installed by any chance or a nonstandard air intake setup? The MAF is a PITA to change out because the windshield cowl has to come off, just like when replacing the intake manifold, so curious if they switched out or tested the MAF while the cowl was off.
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