I finally experienced the dreaded "limp home mode" this morning returning from the grocery store. I pulled over to the side of the road, shut everything down and counted to 10, restarted the engine and the car ran fine the remainder of the trip home.

I grabbed my code reader and headed to the garage, and came back with the following series of codes and brief explanations:

U0401-92 (Intermittent)
U0401-64 (Intermittent)
"Invalid data received from the Engine Control Module / Powertrain Control Module

P2105-00 (Intermittent)
Throttle Actuator Control System

P061A-64 (Historical)
P061A-29 (Historical)
Internal Control Module Torque Performance

U0402-67 (Historic)
Invalid data received from Transmission Control Module

And a non-critical one since it's the wife's seat (hoping for "ejector seat mode" some days):
B0072-1B (Intermittent)
Passenger Safety Belt Pretensioner Deployment Control

I tried logging into Topix to find answers to these items, but the system is no longer granting me access.

Does anyone have any ideas here (besides put the car back on the battery tender) on what the source problem and potential solutions might be?

Thanks in advance for your assistance.

 

Test battery; should have minimum 12.5 volts with ignition off. If not, replace battery and see if DTCs return.

 

P2105 would throw it in limp mode but I would start with NBCat's advice before delving further.

Because the voltage and or resistance of TAC isn't in line with what the ECM is expecting. (e.g. throttle peddle says your at half throttle, TPS thinks you're at idle) so the conflicting info sets the vehicle in limp mode.

 

Thanks, fellas. Battery check forthcoming. FWIW, a new battery AGM was purchased & installed on 6/5/2015, and I keep it on a battery tender if I'm not driving it for a couple of days. Hoping it's as simple as a battery issue because everything else seems ... expensive.

 

Battery fluttered between 11 and 12 volts on my cheap-*** meter. I called Firestone, and there's still pro-rated warranty available on the battery, so I'm heading there tomorrow (hopefully not in limp mode) for a swap out. Fingers crossed that solves the problem. Thanks, fellas.

 

Final note on this saga, and it involves me tossing myself under the bus. The "issue" was the nut holding the CTEK battery tender onto the positive cable lead had spun itself loose, causing an inconsistent (at best) contact when plugging in the battery tender. Small wonder I was experiencing battery related issues as the frigging battery hasn't been receiving an overnight charge in who knows how long and regular driving days are slowing down with the cooling weather.

Hat tip to the good folks at Firestone on 144th & Maple Street in Omaha who had pre-ordered in a replacement battery and prior to swapping it out did a little testing on the battery (it was fine). The service tech noted that the fitment of the charger lead was a little odd, and he could see how it would appear to be tight when it actually wasn't. There was no charge on adding a couple of washers and tightening it down for me, and I was entered into a drawing for a free BMW as a result of having Firestone do a complimentary battery check.

And yes, I'm a natural blond.

 

So codes are gone, problem solved and it was free of charge. That's rare in Jag world.

 

No shyte. I plugged in the code reader yesterday. Gone!