my wife was driving the LR4 today when it went into Restricted Performance Mode. she made it to a parking lot where i met her and checked a few fuses and tested the battery. everything looked good there. my Foxwell NT had some issues communicating with the ecu/bcm, so never was able to pull the codes.

however, after restarting the vehicle, it ran fine and was back in its normal mode. i drove it for 20 minutes and no issues.

some quick reading suggest MAFs and/or fuel pumps. at 142,000 miles i can see it being either or both.

aside from getting a code reader that can communicate with the LR4 better, what else should i be looking at? should i do the MAFs as preventative maintenance? fuel pumps?

 

musical parts is not the most efficient way of dealing with diagnosis and repair.
We really need to see all the codes.

 

if/when it happens again, i'll pull the codes and post them up.

 

If it set a code for MAF or other sensors, it should be recorded on the ECU even if CEL is not illuminated if fit was originally and had restricted performance. Just curious did it happen when car was cold and she accelerated quickly?

 

the Foxwell NT code reader was having issues reading the codes stored.

she had been driving for a while and came off the freeway to a stop light. as she moved on from the stop the Restricted Performance kicked in.

 

cleaned both MAFs with MAF cleaner. so far, so good. acceleration seems to have smoothed out some. i've heard that cleaning these MAFs can cause issues. guess i'll find out soon enough.

 

as it turns out, cleaning the MAFs did not solve the restricted performance issue. when it came back the check engine light came on also, read the code with a generic code reader and got a side A MAF code. i replaced both, saving the old ones.

i'm still getting the restricted performance mode happening every 130-150 miles. the check engine light never comes on and we can get the LR4 to reset itself by turning it off and waiting 10-15 minutes.

will there be codes present even without the check engine light? do i need a LR specific code reader to pull them?

any particular direction i should be looking?

 

pulled some codes today with the Foxwell NT. as I said previously, i cannot pull any codes with the Land Rover specific software but was able to with the generic OBD2 software.

Stored Codes, none
Pending Codes, P0500 Vehicle Speed Sensor A
Permanent Codes, P2135 Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation; U0402 Invalid Data Received From TCM; P2105 Throttle Acuator Control System Forced Engine Shutdown; and, then two (2) more P2135 codes.

 

one thing to check on the LR with multiple random codes is a) battery condition and b) main grounds

 

after doing a little more research and reading i decided to dig into the engine bay the other day. pulled the plug off the TPS and gave both ends a cleaning. i noticed the silicone(?) dust moisture seal was torn and bunched up and simultaneously realized the plug had come off far too easily. i pulled the torn seal out and seated the plug fully and securely on the TPS. two tanks of fuel, these ****ers have tiny fuel tanks, and over 300 miles later and i have had no issues with the Restricted Performance mode. later i'll track down a new/used silicone seal and install it on the plug. my current working hypothesis is that the bunched/torn seal was not allowing the plug to seat properly and giving the occasionally low voltage or improper voltage readings which cause the Restricted Performance mode every 150 miles or so.

the only other thing i did was to turn the LR4 on to the ON position and then depress the skinny pedal 10-15 times. some reading had suggested that this may free up and clear debris in the potentiometer attached to the pedal that syncs up with the TPS.

regardless, i'll update this post as needed.