Hello my name is Mike. I thought I was helping my daughter out with her first car purchase. I probably should have let her do it on her own, although I think she was depending on me. I hopefully wont bore you all and get to the point.

She drove through some water. I replaced a coil and while at it all the plugs. The car has just under 90k on it. The car is in my signature, however it is a 2004 x-type AWD 3.0 and probably something else to go with it but that should suffice.

Now she is getting Intermittent CEL and tranny fault. Pulled code p0121.
It has been a while since the plug change. I have been scouring through the forum the last couple of days and have an idea of possible problems.

You know back in the day it was so much simpler. But I think the powers to be are making more money now that you or your neighbor can't fix just about any problem. Oh well what are you gonna do.

The question...How do I remove the windshield wiper arms? Please help, I do not have a manual. I have done this on other vehicles, but I am not seeing this.

 

Check the connector to the throttle body, it may have been bumped loose.

Then clean the disc in the throttle body,

For codes, just search for the code "p0121". You will see one or the other of
the above actions cured the problem.

 

You may use a pry bar but it may cause damage to the plastic trim. The Wiper-Arm remover is available from Auto-Zone for a small sum.

 

Audio, like was mentioned, take a look at the throttle body and make sure all is good there. The throttle body may just be sticking and a can of throttle body cleaner will do the trick (if you need some guidance of what needs to be done, let me know). The other thing that I would do is to make sure that the plug on the engine side of the throttle body is plugged in firmly and does not have any water inside the plug. The code you are getting is relating to the throttle position sensor which is located on the engine side of the throttle body. It may be that you simply did not get the plug on firmly and now it can make and break electrical contact, making the computer freak out.

 

Good morning to all, and Happy holidays!

Yesterday I had a temporary lapse in intellect, however that happens from time to time. After my post of how to get the wiper arms off I think I had them off before the first reply.

I will check that plug! What are they electrical measurements associated with the throttle body?

I thought based on what I read in some other post that I was uncovering the TCM only to find the wiper motor and a cabin air filter. All is not lost, the filter needed to be changed anyway.

Should I even be concerned with the TCM at this point, based on the TPS code?
If it is worth looking at and for my knowledge where is it located?

Thanks again and happy holidays!
Mike

 

Mike, your problem lies more with the ECU and the TPS than the tranny computer. It is nice to know where the parts are located if in the future you need to access them. But, for the moment, I would not tear anything apart just because.

I would check the TPS plug and the associated wiring. It may be that since you recently did the plugs, the wiring may have gotten damaged and/or is now able to touch something hot. Lets see what you have at that point.

 

An easy way to remove wiper blades is to first undo the nuts and then raise the wiper arm and rock it gently and it will come off the splines Be careful if you drop the arm it can break the wind shield.

 

OOps, Tony;

That sounds like the painful voice of experience ... ?

 

It is the voice of experience but not painful experience.

 

Okay! I pulled the tps connector. From an electrical point of view, ( since that is my trade ) all looks fine. Now I have not started unwrapping wire bundles to see if there is some hidden issue,but that which is visible appears to be fine. I sprayed some electrical parts cleaner on the connections, and put some di-electric grease around the plug body to hopefully prevent any water or other contaminants from being a possible issue.

I am curious though about ohm test or volt test on the tps and connector.
Since I don't have a manual and am not sure of part names, I want to call the apparatus on the other side of the throttle body, the electrical throttle control. Is there any chance this can give this code?

 

Went back out to look over things. There is a check valve between the brake booster and the manifold. It looks as though it has been in the jaws of a pair of pliers. It looks rough externally, but dont know if it is actually an issue or not. However I think it should be replaced while I am at it.

How do you actually get that check valve out of that hard plastic tubing without destroying it?

 

jaghelp.com: Jaguar X-type common vacuum leaks. P0171 and P0174

There is a pic that shows the check valve as number 2. You have to get with the hose not just the little valve. Is not that hard to change.

 

audio, the TPS performs 2 functions in the big picture of things. 1) provides feedback to the computer so it can relate the position of the gas pedal to the position of the throttlebody - remember, this car is drive by wire, not a cable pulling the throttle body open, and 2) provides input to the computer so it can figure out motor loading and work with the TCM to place the tranny in the correct gear based on its shift table.

As for doing an electrical check, I would need to check my drawings to give you the correct pin numbers, but in short, you have 4 pins there and you have 2 rheostats there. If I remember right, they are like 0-500 ohms or something very similar. What you would need to do it is connect up across one of the rheostats and then using your finger, open the butterfly valve. Then all you are doing is watching for a smooth change in the resistance. This is where an analog multimeter would be handy. If you have a digital one, hopefully you have an analog bar on the screen that will help you see any bad spots in the rheostat (which will be marked by jumps in the resistance).

If you need more info, let me know. I can pull up the diagrams and give you specific pin numbers. If you need the diagrams, let me know and send me a PM with your e-mail addy. I will send you all the electrical diagrams for your car. I just need to know if you have an early production 04 (ie, made in March 04 or before) or a later production (April 04 or later). The build date is located in the driver's door jam on the white sticker that is there. There are minor electrical changes that were made during this time. The big one being the numbering of the fuse boxes. I'm sure you can see where that would be a royal PITA.

 

Like I said, all looks fine. I just want to check those items. Obviously this is intermittent, so more than likely if I do a check now , and I am not getting the fault then I wont really know where the real problem is. My thinking is that if it is a bad rheostat, then it would most likely be all the time. However if it was a voltage issue then it ( if the voltages are being sent from ECU ), could be intermittent. Just my thinking, not knowledge. If I check rheostat , and there is smooth transition, then I would need to know voltages.
If it is a volt issue, would these mean a bad ECU, or are there other places to consider?

Also would it be best to remove the throttle body, to clean it?

 

audio, if you have a voltage issue, then you are most likely looking at either a bad connector (which you say looks good) or a wiring issue where the harness has come in contact with something warm and is therefore grounding out. The grounding issue can be discovered by doing a hand over hand of the wiring.

As for cleaning the throttle body, I do mine with it on the car. You can do it with it off of the car. More work since you will also need to break the lines for the coolant system and the like. The big thing to keep in mind that if do it with it installed on the car, odds are, you are going to "flood" the car. The first time you go to start the car, you will want to depress the gas pedal fully (this actually over-rides the fuel injectors and tells the computer to not admit any fuel to the engine) as you go to start the car. Once it starts to catch, you can ease up on the gas pedal and bring the engine to idle. Occasionally you may also get a rich OBD code to pop up too. Reset the codes and then see what you have at that point.

 

Okay< just to update, I found flow chart for checking out various issues. As far as the TPS is concerned I found that the ohm readings between pins 1 & 3 throttle closed should be between .5k to .9k, open should be 2k to 2.4k.
Pins 1 & 2 should be 1.2k to 1.6k closed and 2.1k to 2.5k open.

After performing check my readings were at the lower end for both sets of pins (within tolerances, throttle closed). With the throttle open both sets were about .1k lower than the tolerances. Would this actually be of any alarm?

Next check will be of voltages on pins 2 & 3, both at idle and WOT. Pin 4 does check to have the recommended voltage of 5v.

 

I'm back! I just check voltages of TPS. As far as I can tell they seem to be within the ranges that are needed.

What next, pull the connector from ECU and do an ohm check between both connectors?

Or would unplugging battery do a hard reboot of ECU and maybe rectify the problem?

 

Please see link below for Jaguar electrical wiring diagrams
Jaguar electrical reference

There is a handbook download available in the how to thread at the top of the section.

Hope this helps

Jim

 

Audio, honestly, I think the resistance readings are just fine based on what you are describing. What you would want to do is to run the throttle open and closed a few times to make sure you don't have a dead spot in the TPS. That is sounding more like what you have going on.

 

I am curious if the throttle can be controlled by the foot feed in KOEO, without any issues?
I did notice that while the KOEO, that the throttle motor did have power applied.