Shane, at this point, there is really only one more physical check that you can do. You will need to access the center console and get to the plug for the shifter. It is a 10 pin connector from what I can tell. Look at pins 8 (black wire) and pin 7 (gray wire). You want to do a resistance check between these two pins and with the car in any gear but Reverse, you should have a very high resistance and in Reverse it should drop to under 5 ohms. If you do not get this, then you are looking at your shifter being the source of your issues. If it does drop to a very low resistance when put in Reverse, then you can try putting the car in Reverse (with the key in the RUN position, e-brake set firmly) and then install a jumper wire between Pin 26 (gray wire) on the tranny computer and chassis ground. That will rule out the interconnecting wiring between the shifter and the tranny computer. From there, the signal gets digitized inside the tranny computer, sent over to the instrument cluster (not the GEM, sorry about the confusion) where it is broken back out and grounds out part of the instrument cluster to activate the reverse lights. So, without a more advanced computer, you can not distinguish between the two. This is where a professional shop that can get into the signals inside of the computers can be worth a lot. I would hate to see you start guessing at which computer to replace without at least some logic to why a computer was picked. A used tranny computer is around $200, the instrument cluster is going to be about $100. There may be some programming that is needed if you swap out these parts, so, that will be atleast another $125 or so.

One last check that you can try is getting to the instrument cluster and installing a jumper wire between Pin 3 (green/black wire) and chassis ground. Make sure to get the correct plug as there are multiple plugs back there. This will cause the backup lights to come on if the car is in the RUN position. That will ensure you don't have a wiring problem between the reverse relay and the instrument cluster.

That is all that you can really do. I wish there was more. But, once it goes into the digital land, it ties my hands as to what I can do for you.

 

Thermo, Ok, it's three years after this thread and I'm facing the same problem on my 2004 X-Type 2.5 manual. F2 socket has no power on either side. I've confirmed that the reverse-lamp-switch on the transmission closes contact when my manual transmission is in reverse (with multi-meter).

So, now I am going to follow your step to check resistance on pin 9 of the interior fuse box connector you describe. Am I correct in assuming that I am checking resistance against chassis ground?

 

gShawn, because you have the manual tranny, things are completely different than what this post started out as. There are significant wiring differences between a manual and an auto tranny vehicle.

In your case, I would access the tranny reverse switch again. Disconnect the plug so you can access the 2 wires in the plug. Next, turn the ignition key to the RUN position (do not start the engine). This will apply power to the plug. With the black lead of the multimeter to a good ground point in the engine bay, check both wires for 12 VDC. 1 wire should have 12 VDC, the other should not. If you don't have 12 VDC on either switch, then you have a wiring issue between the plug and the fuse box. If you do have 12 VDC on the one wire, do a resistance check on the wire that does NOT!!!! have power and chassis ground. Are you getting a resistance reading of around 6-10 ohms or are you getting something up above 1K ohm? If you are getting above 1K ohm, then you have an open wire between the plug and the reverse lights or you have 2 bad bulbs.

If you need me to go into more detail, let me know. One tidbit of info I will need though is the month/year that your car was made as you have one of the cars that may have 2 different wiring harnesses in it and there were significant changes made. I do not want to send you on a wild goose chase following things that do not apply to your vehicle. A prime example of this is Fuse F2. In your case, fuse F2 is not used for the reverse lights and therefore is not applicable in your case.

 

Thermo, I've already confirmed that F2 is for the backup lights. First off, it was listed as such in my owner's manual table of fuses; more importantly, I used your suggestion of running power from a known good 12V fuse source to the bottom F2 prong and both of my backup lights lit up.

I ran your suggested test on the trani-reverse-switch connecting socket; I got 12V on 1 pin with ignition on and the other pin had very low resistance to ground (under 10 ohms). I think my next step is to check the relay. The top connector on my interior fuse box is a blue connector, centered and below two black relays. BTW, I have no fuse box in my glove box (to my surprise the plastic door there revealed an open hole). My fuse box is under the dash near the driver's left knee. I want to find that pin 9 you referenced on April 15, 2013.

Thermo, how do you know all of this in such detail?

 

Thermo, this is an accurate depiction of my fuse box. It appears you were referring to connector labeled IP203. I see the location of pin IP203-9 in this diagram.

 

I don't seem to understand this diagram. Shouldn't the reverse-lamp-switch (man tran) be on the opposite side of the relay from the fuse and parking lights? How does IP203-9 get its signal?

 

gShawn, I have all the drawings for the car and being an electronics tech, I understand what the drawings are trying to show and what may not be quite obvious to those that don't work with the drawings all the time.

The drawing that you have above is essentially what I have too. If you look in the middle of the drawing (to the right of the relay), you will see where the lines become dashed. What this means is you have only 1 of 2 of these wired up in the car. Here they were nice enough to list that the top 2 lines are there when you have a manual tranny and the relay line (bottom line) is not there in your case. If you have an auto tranny, the top two lines are not installed in the car.

As for your problem in your car. If you have 12 VDC at the 1 pin to the plug for the tranny switch and if you apply power to the other side and the lights work, then this confirms you either have a bad connection in the switch plug or the wiring between the fuse box and the switch has a high resistance connection in it.

To rule things out, I want you to try something for me. What you will want to do is to get yourself a piece of bare wire about 1-2 inches long that will fit in the openings of the plug from the reverse switch. Bend this wire into a U so it will fit into both spots of the plug (you are bypassing the reverse switch). Now, with the car in RUN (engine off), install the wire into the plug. This will force the reverse lights on. Using your multimeter, measure the voltage on the bare piece of wire. Do you have 12 VDC on this bare wire? If no, then your problem is in the wiring between the fuse box and the plug. if you do have 12 VDC (and the reverse lights are on), then you have a connector issue and you are not getting good connection in the plug on the reverse switch. You can use a small screw driver to bend the clips back out to ensure you are getting good connection. You can also pull the pins out of the plug (there is normally a small metal sliver on one side that locks the pin into place, depress it as you pull the wiring out the back of the plug). From there you can clean up the plug to get it shiny silver again and bend the clips to make sure they make good connection.

If you need more help let me know. I have been playing with cars since I was 6. So, 40 years of tearing who knows what apart, you learn a few things. Having a back ground in electronics is making working on modern day cars that much easier. Having a "no fear" attitude when working on cars is a nice plus too when tackling things that are new. As for Jaguar info, I have collected stuff over the years. If there is something that you are after, let me know. I may have it. Most if it is simply knowing what the drawings are telling you as the information is not necessarily all in the same location and you are having to put multiple pieces together to get the whole picture.

 

Thermo, Ok, now I seem to have gone from frustrated to pissed (certainly not at you – just the situation). I did the test you suggested to short the connector for the revers- lamp-switch and sure enough, the reverse lights came on. Since I had earlier tested the reverse switch as good, I figured I must have a problem with the connector making contact with the switch.

I Jerry-rigged a Molex connector and cable to attach to the switch and then assured contact with the connector, adding another disconnect in-between. No go. I’m getting some resistance from the switch of about 100 ohms (tested at my newly installed disconnect between the switch and connector). I had less resistance when the switch was tested out of the car, but I guess I was pushing harder. Perhaps the lever from the manual tranny does not fully depress the switch. 100 Ohms does not seem like a lot of resistance to prevent the lights from functioning. I can short my newly installed disconnect and the reverse lights come on. What do you think? Is it a relay issue that now needs less resistance to work or a switch issue which perhaps would close further creating less resistance?

Oh ya, another related question. How long will heat-shrink tubing hold up in an engine compartment. Does it continue shrinking until it cracks apart?

 

Shawn, from what you are describing, it is sounding like the switch is your issue. THink of it this way (hopefully this will make sense to you). Any series electrical circuit is really a big voltage divider circuit. Things with higher resistance drop more voltage and things with less resistance drop less. So, using your car as an example, your reverse lights are 10 ohms and with the switch coming in at 100 ohms, that would mean that the circuit has a total resistance of 110 ohms. This would mean that the switch would drop 10 volts (rounding) and the reverse lights would drop 1 volt (rounding). 1 volt is not enough to make the reverse lights light up (hence why they are dark). The reverse lights need around 10 volts to make adequate light.

As for heat shrink, most of what you can buy will survive in the engine bay just fine. If you are really worried about it, find some stuff called "Raychem". The stuff that I have in mind is model "WCSF". If you look on e-bay and do a search on "raychem wcsf", you wil find some listings. The number after the WCSF is the shunk value in thousandsth of an inch (ie, WCSF-070 would be an inner heat shrink diameter of 0.070" when it is shrunk down). This stuff I can garantee will survive in your engine bay. I use it at work to survive a nuclear core melt down. I think that might be just slightly worst than the conditions in the engine bay. In most cases, the WCSF-070 will be what you will need for most of your situations.

 

Thermo, I thought this reverse-switch circuit was driving a relay, rather than the lights directly. Regardless, I can now resolve this.

For other North Americans following this thread, the reverse-lamp switch (aka back-up light switch) is a Ford part number XS4T-15520-AA, also used in the Ford Focus and Ford Cougar since the late 1990s and numerous Volvos since 2004.

I found one at my preferred vendor Rock Auto (RockAuto.com) for $ 12.98 and under $3 shpg.
2001 FORD FOCUS 2.0L L4 SOHC
Electrical-Switch & Relay : Back Up Lamp Switch
STANDARD MOTOR PRODUCTS # LS328

 

I use the hi-temp wire loom on any questionable wiring in my cars. I especially use it on custom wiring installs. Also "neats up" the engine bay and other related areas. The plastic zip ties are also good at holding wiring away from unwanted areas.

 

Shawn, you are correct for automatic tranny vehicles. For those vehicles with a manual tranny, the switch is acting as the relay. Manual tranny cars have no relay. Remember me saying that the drawings will sometimes show more than is really there and you have to pay attention to what the drawings say. This is one of those cases.

 

hlgeorge, I really like the look of your Claret XK Jag.

 

Thermo, Ok I got it working with a kludgy install of a 12V 30A Auto-relay I had on hand to use the high-resistance reverse-switch to close contact with the wire-harness connector. I ordered another reverse-switch and plan to remove my kludge once it arrives and proves effective. Regardless I passed inspection today, so mission accomplished!

Yes, I was confused by the drawing and stated I didn't understand it thinking it didn't make sense to have the switch on the same side of the relay as the lights. You now explain that the relay is irrelevant for a manual tranny; I guess the diagram does now make sense. I really appreciate your help along the way. I am pretty savvy with electronics and I know my way around cars, although new to Jags, but I consider you some kind of Jag electronic savant. I really appreciate your detailed and constructive feedback. Not only how you have helped me, but I’ve notice how many others you’ve also help. You deserve some recognition my friend and if you make it out to beautiful Southern California, I owe at least a good drink or a coffee if you prefer overlooking an ocean vista. Truly!

 

gShawn, had this been 10 years ago, I would have been in and out of San Diego more times in a year than I care to admit to. Being in the navy at the time, my boat loved pulling into San Diego. For awhile San Diego seemed like a second home to me. Too bad my favorite restaurant in Old Town went out of business (Pico de Gallo as I recall). Granted, there was a really nice italian restaurant right next to it. If you go there, get their jalapeno fettuccine. Not really hot but man is it good. I have now started making my own, but I toss in some bacon with it just to make it my own little creation.

As for being an electronic "savant", by no means am I one. I had an X-Type and when I get vehicles, I tend to learn as much as I can about them. I was simply passing on what I have gathered over the years. I find it "fun" diagnosing vehicles over the internet and helping people get them back on the road.