I got my new iCarsoft LR V2.0 and plugged it in and got the P1251 code and the message "Throttle motor relay off malfunction". I pulled up a pdf with entitled 2001 XK8 Relay and Fuse Box locations. It shows 2 throttle motor power relays, one on the driver's side one on the passenger side inside the compartment under each of the panels with the pull up hole. However, when I open the driver's side panel I'm not seeing those relays. Am I mistaken as to where to look?




There are numerous relays in the fuse box on that side of the engine compartment but none of those are the throttle motor relay according to the layout in the first picture.



Am I looking in the wrong place or is the relay layout I'm looking at not correct? I've got to get this throttle motor relay resolved before I can take the car to get smogged to get it registered.

Joe

 

The diagram clearly shows the THROTTLE MOTOR POWER RELAY just forward of the ENGINE COMPARTMENT / CONTROL MODULE ENCLOSURE.

You are looking on the wrong side of the car.

 

Hi Bob,

I missed the (RHD) and (LHD) on the diagram. I did find it in the compartment on the other side. The throttle body relay is a 5 pin relay, Bueler part no. BU-5084-0000. I have a few new relays but they're "Multi Purpose" 4 pin ones so I'm going to run to the store and pick up a replacement 5 pin and see if that solves the problem. I did notice that the socket on the car does not have a connection for the 5th pin to connect to. Should this actually be a 4 pin relay?

I just found the 2001 XK8 Wiring Guide and when I go to the engine management section the throttle body relay appears to be a 4 pin relay.



So is this Bueler relay a replacement that was put in at some point? Can I use one of the 4 pin relays that I have?

Any else that would cause that code on the scanner?

Joe

 

All BROWN X308/X100 relays are 4 pin.
I have no idea (or heard of) Beuller relays.
I have heard 1986 Ben Stein call "BEULLER, BEULLER.........."

 

Well they obviously exist, I've got a fuse box full of them. I'm just looking for some help here with what could cause that fault code message. I guess I'll head over to my dealer on Monday and purchase one of their overpriced OEM relays and see if that works.
In the mean time if anyone has any other ideas what caused that message please let me know.

 

Just swap another less important relay in the throttle spot?
They all look the same.

 

Just be aware that the OEM relays have a flyback resistor in them to stop back EMF from potentially damaging your electronics - make sure you replace the relay with one that is the same spec as the original - the number of pins isn't so important as whether or not they have the resistor. You can see the resistor shown on the wiring diagram parallel with the coil. You might want to check if those Bueller relays are in fact suitable for the Jaguar.

 

Hey Dibbit,

thank you for the information. I’ll check with someone Monday about the relay having a resistor. I’m not sure who replaced them but they all seem to be Bueler relays. The diagnostic I ran only showed a problem with this one relay. I have several new 4 pin relays, I’ll check to see what the resistance is across them. I’ve been looking through the schematic but can’t find any info on what size resistor that is.

Joe

 

These are the relays that I have: https://apaindustries.com/parts/16504 According to the website they are OEM replacements for the Jaguar relay T4N15704, which is what the Jaguar parts website says was in there originally. I plugged it in and the check engine light went out. (it came on this morning when I started the car up, although when I drove home last night it was not on). The OBD2 gives me the same error code/message. I neglected to mention that this originally started when I took the car in to get a smog certificate and the tech there used his OBD2 and got the message P1251 Air Mixture Solenoid Circuit Malfunction. That message was replaced by the one I now have about the relay. I get no other code/message. (other than a message about the trunk lock that I know about, the usual broken wire for the trunk push button)

Joe

 

Let me ask a question out of school. The throttle motor controls not only the idle, but all movement of the throttle butterfly. Is that correct? If the relay malfunctioned, wouldn't the throttle motor stop working entirely? Rendering the car undriveable?

 

What if the fault is very intermittent.(faulty open circuit/bad connection)
A few micro-seconds of OPEN CIRCUIT and the DTC is logged.
You will not feel any loss of response for a brief open circuit.

Just guessing.

 

As far as I can tell those are the correct relays for the car - if they have a pinout diagram on the side look to see if they show the resistor in parallel with the coil.

 

There's not diagram on the unit or the packaging or the website. I'll have to call on Tuesday, forgot today is a holiday.

I forgot we were going out of town so I didn't get the clear the codes and retest after I put the relay in. I'll check it in the morning and see what I get. In the mean time the car sat in the parking lot out side at the casino/hotel and when I got in this morning it started right up, no messages, no check engine light. Weird. I did read a thread indicating that it might be possible that the starter motor might be going and pulling too many amps at start up and thus not leaving sufficient power for all the computer checks and, therefore, it throws out those messages and turns on the check engine light. I guess I can throw the multi meter on the battery and see how many amps the starter is pulling when I first start the car.

Joe

 

First of all, happy to be here
My steering wheel is on the left is the diagram you posted for the steering wheel on the right?

 

2005XK8 convertible got hot shut it down very quickly replace the cross pipe and the water pump old water pump wasn’t missing any of the plastic fins replaced it with the metal fins with twice it got hot after it cooled down just to get it where I can work on it tried to start it and it wouldn’t start. It ran perfectly. I shut it down and now it won’t start. I think I unplugged three sensors, two hoses and eight bolts.

 

The diagram covers both - look where it says LHD and RHD. It can be confusing if you don't notice.

 

Put the OBD2 scanner on this morning and cleared the codes. Ran the diagnostics again and no codes or messages. (Well there's still the message about the trunk lock circuit but I know what that is). Now I just have to put a few hundred miles on it so I can take it to the smog station. I should have done the rest before leaving for San Diego on Sunday. Ah well, guess I'll just have to drive it more

I also watched a video regarding the headrest issue, the passenger side one doesn't move. So I guess I'm taking the seat back skin off, or at least partially, later today.

Joe

 

So this is the third time I've gone to the smog station and have been told that I need to put more miles on the car so the smog check can be done. When he puts this obd2 on the car he gets the below messages. CCM, CAT & EVAP read INC. Anyone know how much mileage it takes to clear the code reset ?

Joe

 

Here's a conundrum. In CA you can pass if all monitors are set except EVAP. However, you'll never get the CCM to set unless all monitors are ready, including EVAP. The CCM gives you the P1000 code or the P1111 codes. I posted a link somewhere from CARB saying the CCM was to be ignored, but I can no longer find that.

Anyway, you have two issues, and you may need a better scanner. When I got mine, I got it smogged eventually with EVAP not ready. Using a better scan tool I found an error for open circuit on the canister control valve at the back of the car. It had failed, but no CEL light because the computer couldn't run the EVAP test. Dummy me decided to fix it and then the CELs started. I replaced the purge control valve under the left fender, a common failure. Then chased "minor leak" codess until I found a cracked charcoal canister. I replaced it and EVAP set quickly. So, in your case, you may have a similar issue. A failed CCV will cause EVAP to not set but will throw no codes. If the EVAP test runs and it finds a leak, it WILL throw a code.

The second problem is your CAT monitor. These are harder to fix. The downstream O2 sensor has to detect a significant increase in temp from the cat inlet. It then knows the cat is performing. If it doesn't, the monitor won't set. If it did set, and it stopped sensing that temp increase, the car would throw an 0420 code, cat efficiency. Anyway, the problem could be a bum downstream O2 sensor, it could possibly be a bum upstream sensor, or it could be a bad cat. The problem may be in finding which cat. You may have other pending codes for mixture, etc., but you may not.

You can try using Cataclean a couple of times. I've used it to get stubborn monitors to set on marginal cats. You can also try installing a spark plug anti-fouler onto the downstream O2 sensor. Yes, it's illegal but the way these cats are wedged in, one would have a difficult time spotting it during a visual inspection, if your smog shop even bothers. Of course, should all else fail, a zillion dollar cat may be in your future.

 

Hey there Y2K. I found something called Drive Cycle Procedures that tells you what to do after clearing any error codes on an OBD2. https://www.obd-codes.com/jaguar-drive-cycle

The picture I posted was the smog station's OBD2, not mine. It sounds like I'm going to have to take the car out on the freeway for a road trip before I can get it smog checked. So far I've been driving it but only around town so I'm not getting the rpms up high enough according to the procedures. I should have done the reset when I was down in San Diego, but, . . .

I'll just keep on driving and see what happens. It's a royal pain because I can't transfer title until I get a smog check.