mindofitsown

Thanks Joe, I will have to see if I can get that at some point. Good news! Passed MOT with new sensor. CO at 0.00%. HC at 0ppm and Lambda at 1.007 so almost perfect. Should find my mpg get back to normal soon to boot. Thanks to everyone for your help and I promise to listen in and contribute more to the forum. P.S. don't think that will be long since one of my key fobs has gone down today and new battery has not solved it.

Forgot to ask.....what is 'JTIS', regards, Dennis

Thanks Joe, absolutely bang on. That was the sensor indeed. Very useful information supplied, many many thanks.

Sorry Russ, that should have read "stoichiometric ratio index" which I have since researched to mean the ratio of mass air flow to mass fuel flow, the result then divided by 14.7. Apparently, the ideal ratio of air to fuel in a petrol engine is 14.7 (when hot) and thus if we achieve the ideal and then divide by the constant 14.7 it will end up as 1.0 as an index which the MOT calls Lambda. Less than 1.0 means too little air for the amount of fuel (i.e. rich mixture) and greater than 1.0 means the opposite (i.e. lean). I guess I am teaching my granny to suck eggs for many of the contributors on this forum but I want to air my thoughts of what's going on and invite correction so that I get it right. Good news! I have renewed the upstream O2 sensor on Bank 1 (as per code P1646 description) and all is well! The old sensor was easy to remove (luckily)and now I have sensible O2 readings and the fuel systems go to "CL" (closed loop) mode with active fuel trimming. I have cleared the old code and the MIL lamp stays off. Relief! Got MOT re-test later in week so fingers crossed and will let you know the result.

Thanks all who have provided hints and tips thus far,it really is appreciated. The latest news in this saga is as follows: Battery disconnection/reconnection didn't really make much difference but worth a try. Bought a cheap code reader and got codes P1111 (Intake Air Temperature Sensor Circuit Intermittent High Voltage) and P1646 (O2 Sensor Malfunction Bank 1 Upstream). Note, this is less than a week from taking it to local Jag dealer who charged me nearly £100 simply to say the ECU 'won't communicate'. Grrrr! After clearing codes, the P1646 re-appeared soon after with MIL light back on again. Looked into various forums and found contradictory posts about which bank and whether it really was upstream/downstream etc. Decided to look further in code reader with real time data whilst driving. Found that Fuel Systems 1 and 2 stay in "OL" mode whatever happens. Also found Fuel Trims stay fixed at 0% and both downstream O2 sensors have 'stuck' readings (for current and voltage readings) that occasionally become unstuck and then stuck again. Checked o2 sensor fuse and relay and they are fine. Worked out (I think) what some of the cypher language used by the code reader actually means. (had to do this because the instruction manual doesn't cover this and its taken me most of the weekend). I think what is supposed to happen is that the after start up, the ECU causes the engine to default into "OL" (open loop? control mode i.e. no sensor feedback to make adjustments). After about 15 seconds or so, the sensors have been read and providing there are sensible readings, the ECU goes into "CL" (closed loop? mode i.e. thereafter making adjustments to fuel inputs via the injectors, on a near continuous basis according to feedback from the sensors (MAF, MAP, O2 etc.).The adjustments are called "short/long term fuel trims" and are measured as a percentage from the open loop default value and these adjustments help ensure minimum CO emission and as close to a Lambda (stoichiometric ration index) of 1.0 as reasonable. The problem in my case is that the CO is too high (1.5%) hence failing the emissions test. Now, 1.5% would have been a good result for my old 245DL Volvo from 1980 which was permitted up to 3.5% but that old skool vehicle was designed as open loop. I thinks what is going on is simply that the ECU does not get sensible values from the O2 sensor(s) at start up and as a result it stays in "OL" mode which causes the fuel trims to stay fixed at 0.0% i.e. the ECU simply ignores the sensors and thus no adjustment are made. So, with what I can make out to be sensible readings for Mass Air Flow, Manifold Pressure, Throttle Position and non-sensible readings from O2 sensors I have just ordered a whole new set of O2 sensors (simply can't get enough clear information about which sensor is duff). Will post again with result of replacements. Regards.

Many thanks Peter and Carole. There is another possibility in that I jump started my partner's car last month without having the engine on and I wonder if the sudden drop in battery voltage has caused the ECU to throw a wobbly and I have unknowingly been driving around in 'limp home mode'. Does anyone know what warnings/messages are given if this were the case? Regards, Dennis

Firstly my apologies for not contributing to this great forum for some time and only now that I need help. Problem is my beloved S type (3.0 V6 53 plate) failed MOT solely on emissions. High Co =1.5%, (limit 0.3%) and low Lambda 0.96, (limit 0.97).Have noticed petrol consumption increase of some 25% in last month but still drives smooth, if that helps. Note, this time last year (with same MOT firm and 9000 miles back), CO=0.0%, Lambda 1.014 Lots of theories, so took it to Jag Dealer for codes to be read and guess what, car ECU would not communicate with diagnostic software (although other electronics would). Now £100 down just to find that out. I am at a loss and desperately need help to get my baby back on the road. Begging for help! Regards

I'm sure Paul's excellent post represents a 'leap' forward with regard to retrofitting techniques and long may it continue. My problem (and I suspect some others too) is that I'm already confused even when things are explained at an apparently basic level due to my dinosaur knowledge of current technology. My situation is frustrating in that currently I have to pull into a layby to make/take a call. My previous vehicle (an old Primera) had a stereo fitted that enabled Bluetooth connection to my phone and that was great (even though I had to re-pair each time I used the car). All I want is the same capability through my S type audio system. The question is can it be done without ripping out the existing audio system and how expensive would it be? Vehicle is 2003 model with touch screen satnav. I don't have Jag Voice module nor Bluetooth module (I think) nor ACM (I think) and as for 'D2B' optical fibre, well I have no idea. I am tempted to buy one of those 'Geartist' gizmos which I think works as follows: I somehow 'pair' my phone to the device using Bluetooth and then it transmits on an unused FM channel to my existing radio and thus through the speakers. What happens if I'm listening to a different channel when the phone rings, baffles me (do I change channels when it rings?) How it picks up my voice other than through the phone microphone while it sits in the ashtray, is also an unknown to me. Please forgive my primitive understanding of all this but it doesn't help when Jaguar provide a phone button on the steering wheel that doesn't actually mean what it says. Any help from this most excellent would be most appreciated. Kind regards, Dennis

Welcome Chris. I can't help much with your technical problems but Jags seem to run in family lines. My son's Jag is almost identical to mine, same model, year, colour and nearly the same mileage (70kish). Only difference is that mine has the touch screen satnav (ha!) and his has the door protector strips (grrr!).

Hmmm... I would be careful about cheap discs. I followed some threads on this a year ago and decided to buy the latest version off the net to replace my original 2003. Whilst it loaded OK, it was exactly the same map as the 2003 i.e. still doesn't recognise streets built more than 10 years ago. I should have moaned at them but it was only £20 or so.

Colin, I understood from an earlier posting you had the car returned to you and all is fine except the garage did not replace air con gas. I presume you got this done? But, even so, why did the garage have any need to touch the air con system for a DCCV fault? I say this because, as I understand it, the DCCV does not actually have any connection to the air con system. It simply controls the heater matrix, whether to allow coolant to the heater or not, depending on temperature selection. If we are to assume that the air con system is ok then there still exist a problem with controlling the heater valve. When working normally, the DCCV is NOT energised to give heat and conversely, energised to stop heat .So if you can't stop heating coming through then either the wiring to the DCCV is faulty or, the DCCV itself (unlikely as just been replaced) or the CCM is not working (unlikely if just repaired). The only other possibility is the +12V supply to the valves if say the 10A fuse is blown (perhaps from previous fault). I believe the fuse supplies other circuits so you may have to investigate what the other circuits do in order to look for further symptoms. Hope this helps. regards.

@ Colin, many thanks for that info, I will look them up. @Phil, I meant that my other half wouldn't stand for it having car bits on the sofa. Soon I will be moving house and the new place has got a perfect 'man-cave' attached to the garage which I can't wait to kit out and have as many parts lying around as I like.

@ Colin, Can I ask you which outfit in Swansea you used to fix CCM (and whether they added over-current protection)? @ Phil, You put your spare CCM on the sofa! Wish I could get away with that.

Gosh! Those sills are even more shocking! Interesting how different peoples' backgrounds impact on their fears/confidence. Those sills would frighten me to death but clearly don't scare you with your experience. The whole forum now knows who to contact for welding issues ...haha! I was trying to establish if ALL plugs gave no spark. If that is the case then although the coil packs are suspect, it may indicate a primary problem with the ECU not providing pulses to the coil packs. This might be for a variety of reasons but quite often is caused by a sensor input (needed by the computer to issue pulses) not being present. A classic is the crankshaft position sensor for instance which can be quite cheap but cause mayhem. Let us know how you get on with a coil pack check first. Regards.

I think I found the problem. Some weeks ago when I replaced the DCCV valve, I noticed that electrical control of the new valve was not working on the driver's side (the old defective valve had damaged the CCM). I have not got round to extracting the CCM to repair it and install an overcurrent protection circuit as yet. So in the mean time (to switch off heating and provide A/C) I hooked up a temporary circuit from the valve control pin to ground via a fuse and a switch (the latter inside and accessible from driver's seat). This enabled some control over heating/cooling. What I didn't realise is that the +12v feed to the valve is permanent i.e. not via the ignition but straight from the battery (via a fuse) ALL the time (nasty design). So, when leaving my temporary arrangement switched for A/C and exiting the car, about 0.75A of current was being drawn from the battery when sitting on the driveway!. Hence, over a night or two it would drain the battery (and I bought a new battery for no reason arrrrgh!). Until I fix the CCM electronics I will just have to remember to switch to heat before leaving the car. Moral of the story, don't assume any logical design with the Jag which would have ensured unnecessary circuits when parked were switched off via the ignition key.