P0102 / P0730 / U0401 codes..HELP
 

I just had to replace some coils and had it done in a shop because I now live in a FL condo and we can do no work on cars anywhere here.. The car has run fine for a week then yesterday on start up on return from shopping I had an amber dash light with “ABS Fault” and “DSC not available” and “Cruise not available” on the display but drove home without a problem.. Shortly after I had to make another short .5mi trip and as soon as I left the gate more trouble where the brakes or the trans felt like I hit the breaks for a split second but I didn’t so I went right back and hooked up my iCarsoft…the codes are 1) ABS control module U0401 “invalid data from engine control module or power control mod”. 2) Power train code P0102 “mass or volume air flow low input. 3) Trans mission code P0730 “incorrect gear ratio”. After the having the breaks apply without touching them I fear even driving it to a shop.The breaking jerk was so brief it could have been the transmission getting an erroneous signal and feeling like breaks. I need advice on this. Thank you all very much.

How old is your battery. Classic signs of a failing battery!

Thanks very much...It's about 1.5yrs old and it's the first thing I'm going to ck at daylight.. I'll be at the battery with my volt meter while my wife cranks the engine to see how far the volts drop with the starting load. Be back shortly with a report.

Thanks..I just did the crank load test and the battery dropped to below 10v instantly with the load so a known good battery is the first step.. The battery is out and in my van, under warranty and will be done within a hour and I'll go from there and will ck the charging system.

Was that battery fully charged? It may be perfectly fine healthwise, just partially run down. The crank load test is only accurate with a fully charged battery.

For example. Our 2005 MY, 3.0. Morning voltage check, 50+ degrees, vehicle not running, open trunk, light on 12.21. Start vehicle, radio on, HVAC on automatic at 74 degrees, 15.26 at start up. Engine warm and running 10 minutes 13.39.

Taken just this morning.

https://cimg8.ibsrv.net/gimg/www.jag...a9eef35202.jpg
https://cimg7.ibsrv.net/gimg/www.jag...1cd387828f.jpg

I also learned long ago we have to start with a known good battery so I just got back from a recharge and good battery test and put the same battery back in. I had 12.59v standing and 15.20v running/charging.Should be good right?
Started the car and the only thing left on the dash screen was ABS fault.. I went through my iCarsoft and dumped the power train ,trans and ABS codes caused by low voltage but the dash screen then said "hold foot brake and park".. I took me a second to realize the park is the chrome flip up switch center console. Did that and everything is normal. I'll get back soon as I drive it some and thank y'all again.

Thanks for tuning back in.. The Walmart Everstart Maxx H8 900 CCA tested at the store measured 786 CCA and 12.75 volts on the auto charge / test machine..The print out said "good battery,return to customer" so I reinstalled it.. I'm still thinking I might just have a voltage problem. When I search "Jaguar S type “ABS Fault” and “DSC not available” and “Cruise not available”all together it's amazing they come up all together or at lease 2 of them..anyway many results point to voltage drop gremlins but some point to a wheel speed sensor. The battery sat overnight and had 12.29 volts and dropped to 11 volts briefly cranking just before starting and the gremlins returned as soon as I drove 50ft. Does anyone know the threshold low voltage where the gremlins attack. Then again it could be a wheel sensor. I found 3 cases where that was it. One case where it was a $900 throttle body I think. Ouch!, and one said he cleaned his mass air flow sensor and it fixed it..These gremlins are elusive. Do I need a better battery? I read some positive reports about the Everstart Maxx H8 from Jag owners but I still have questions about the standing 12.29v dropping to 11v while cranking.. I just don't know enough..thanks for your thoughts.

Sure sounds like a failing battery to me....

I have received spurious error codes at 12.15 volts... YMMV.

Thank you ... I found several recommendations for the Bosch battery so I bought their best blue top AGM for $219. It had a new standing voltage of 12.46volts.. I installed it and started the car and got the same "break assist fault" , "ABS fault" .. "Cruise not available" .. "DSC not available" along with "break switch ststus" on the dash warnings. I hooked the iCarsoft up and none of the codes in the title that I canceled last time came back but I searched the iCarsoft menu farther and found a code for "rear left wheel speed sensor". Could that one part have been the cause of all these dash messages and ABS light on?
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I looked on ebay where there is one for $217 and the rest are like $17-$20..https://www.ebay.com/sch/i.html?_nkw...speed%20sensor
I called 2 auto parts stores and one said $150 and the other was over $200 for the sensor... I bought one on Amazon with a 5*review for $16.64...

Anything is possible given the electrical system in these Jaguars. Without a strong battery, spurious codes are almost automatic. I would write the codes down, clear them all with my iCarsoft scanner, and do some more driving to see what happens....

I would also swap the positions of my rear wheel speed sensors to see if the code thrown follows the swap....

If it's not a transient fault, maybe. The ABS sensors are used to be sure about speed & braking so can suppress cruise control. Bound to affect DSC too.

12.46V sounds considerably too low. Did you fully charge the new battery and measure at its terminals (after dissipating any surface charge)?

Thank you both for your time.. I finally figured out the wheel sensor code was stored in the ABS on Icarsoft where I deleted it the first time but all the messages stayed on the dash because it was also in the powertrain file.(wierd). when I deleted it there also the dash was clean / normal but then I drove out the gate and 100yds down the road all the dash warnings started from the speed sensor.. Everything is happy here though with a new sensor on the way. Walmart gave me all my money back for the 1yr old battery even with no receipt and I may have a better battery now. The guaranty 48mos.

Way to go Walmart!

Hopefully all will be well with the new sensor - let us know please.

Because the car has a CAN system all modules communicate with each other and codes get passed through along the way...sometimes a code will register with a module that does not seem related....it gets Gremlins also, but you have to use jlr sdd to get the comm network reset....I recently had a u code showing on 5 modules....the root problem ended up being the audio module had lost it's configuration...it happens to be a network gateway....sdd fixed it....but strange how the CAN network is routed....if you want good diagrams use Gus's site....jagrepair.com

I learned about the CAN system this time when I couldn't get the ABS light off after deleting the code then I found the same code in two more places. I hope when I get the left rear wheel speed sensor in and delete all the codes they won't come back. I don't have a jlr sdd, only the iCarsoft. I read several who had the same trouble who installed the new sensor and fixed it with no mention of the comm network reset but all were 5 star Amazon reviews of people that bought that sensor from that seller. Fingers crossed. Thanks Scott

If I do need the JLR SDD there are downloads on ebay for less than $20. Not sure at all if they are good or not but I'll wait until the sensor is in and go from there..

All codes were created by the left rear speed sensor and shared through what I learned here is the CAN system. R&R the sensor did the trick.