Hi Guys, changed both up stream sensors so i could pass smog. the drive cycles never completed to even be ready to take a smog check. drove the car past week 587 miles .then it threw these codesp021 throttle switch a p0460 fuel level sensor a switch p171 to lean bank 1p174 to lean bank 2. any help with this would be greatly appreciated. car has a slight miss when you step on gas like its sucking air then jumps into smooth acceleration real suttle you dont even feel it when your accelerating. i m thinking electrical like a wire grounding out just dont know where to start. things ive done changed all the coils new plugs maf sensor smoke test no leaks. a point in the right direction or sollution would be awesome have to get the car smoged. again thanks for all your help greatly appreciated

 

RANT BEGINS>>>>>
Are you wondering why 76 other members have viewed your post so far but 0 have replied?

its a regular issue so it cant be lack of knowledge. let me tell you. a single block of text with no line breaks and no capital letters at the beginning of sentences is extremely difficult to read. most of us can scan through a post rapidly understand it and get to the root of the question but a single block of text usually has to be reread it to make sense of it. add to this giving inaccurate diagnostic trouble codes. it soon gets to the point where readers start to think i cant be bothered and move on to something else. it's not that many of the members wont know the answer or be able to suggest possible solutions but if you cant be bothered to take the effort to make it easy for readers then dont be surprised if they dont want to make the effort to help you out. compare my version of your post.

I haven't changed any spelling or corrected the invalid DTC's - just added full stops (I think you call these "periods" in the US) and logical spacing. You have to agree that's a lot easier to read.
<<<<<RANT ENDS

Graham

 

Let's see if we can get some progress on this for you.

First, the DTC's (error codes). P0460 is a valid code and your P171 and P174 are just missing the leading zero. I think your P021 is likely to be P0121:

P0121 - TPS circuit range / performance
P0171 - A bank combustion too lean
P0174 - B bank combustion too lean
P0460 - Fuel level sense signal performance

The possible causes of P0171 and P0174 are:
1. Engine misfire
2. Air intake leak between MAFS and throttle
3. Fuel filter, system blockage
4. Fuel injector blockage
5. Fuel pressure regulator failure (low fuel pressure)
6. Low fuel pump output
7. HO2S harness wiring condition fault
8. Exhaust leak (before catalyst)
9. ECM receiving incorrect signal from one or more of the following components: ECTS, MAFS, IATS, TPS

The possible causes of P0460 are:
1. Fuel level sensor to instrument pack circuits intermittent short or open circuit, high resistance
2. Fuel level sensor failure
3. Instrument pack fault (incorrect fuel level data)

The possible causes of P0121 are:
1. TPS to ECM wiring open circuit or high resistance
2. TPS to ECM sensing circuits (“1” or “2“) short circuit to B+ voltage
3. TPS failure

You mentioned "drive cycles". Did you carry out actual "Drive Cycles" as detailed elsewhere on the forum or do you mean the Monitoring Tests have not completed?

Graham

 

Thank you appreciate you much!

 

Awesomesauce! Thanks again for correcting my grammar. And your knowledge of the codes. Will do my best to relay my thoughts better. Where. So you Guys can assist.

 

In regards your drive cycles question. I meant monitors have not completed

 

That's two different things. Drive Cycles are a deliberate driving pattern or style used to complete the Monitoring Tests in the shortest possible time. The tests will eventually complete just by driving the vehicle but, as you have already discovered by 587 miles of normal driving without them completing, this can take a huge time and distance.

The Drive Cycles are detailed in the attached PDF. You will travel a lot less miles but the problem is usually finding a suitable stretch of road to follow the required driving patterns.

The DTC's you listed are still an issue. The most regular cause of both P0171 and P0174 is air leaks between MAF and Throttle Body and this should be the first one to check and eliminate. You didn't confirm if I was correct in interpreting the p021 you listed in your first post as meaning P0121? If so, the worrying one of the possible causes is TPS failure. This is the black sensor on the side of the Throttle Body. When I had my 2001 XK8, the TPS was not available separately which meant a replacement Throttle Body when the sensor failed. I understand from several posts in XK8/XKR forum that the sensors can now be obtained.

Graham