I have a 2000 Jaguar Vanden Plas. I recently replaced all the coil packs, MAF and spark plugs and it has been running great. I was freeway driving and the outside temp was 113 degrees. The car went into restricted performance mode. It had no power. I could accelerate slowly and gain speed but it would take about 2 miles to get to freeway speed. When I got closer to home where it was only 95 degrees, it went in and out of restricted performance mode and then ran fine again. I have a code reader and there are no stored or pending codes. I would love any advice from those that know better than I. I am very confused why there are no DTC's. Thanks in advance.

 

Engine coolant sensors are prone to failing without a code and shut the car down, I wonder if yours is the case as you point out temps it may work at lower temps but higher it struggles, maybe try and replicate the fault with the code reader plugged in.

 

I like Sean's theory about the ECTS.

Just to offer another possibility, Restricted Performance can be caused by a problem with a wheel speed sensor or solder joints in the ABS/DSC module. The diagnostic trouble codes that are flagged have a C- prefix (for Chassis) and cannot be read by many generic OBDII code readers that can only read P (Powertrain) codes. Typically you will see the ABS/DSC warning lamp in conjunction with the RP. By the way, RP may lock the transmission in one gear (3rd or 5th) and/or restrict the engine speed to 3,000 rpm, which could be why you felt the engine had no power.

I still like Sean's theory better given your suspicion that the ambient temps may have contributed to the problem.

Cheers,

Don

 

smmccormack Clean all the contacts on engine bay (computers connectors, all fuse boxes, ABS connector). It works for me.

 

Hmmm
Reading this has got me thinking about my little problem, on my V8 s-type, also lack of power and no codes thrown.
While I was driving monitoring the coolant temps, the readings where bouncing all over the place, they read as high as 424* F, I know that's impossible of course, then into the 300's, then normal between 190 and 215, then back up again and so on, so concluded that the temp sensor is faulty or a wiring problem.
Haven't replaced the sensor yet but will tomorrow.

 

I think it doesn't work as you should have P1111 or P1000.

 

For some reason, not all OBDII scanners show the readiness monitor codes P1111 or P1000. The Torque Pro app used with an ELM327 Bluetooth adapter usually does, and you can get both for about USD $15.

Cheers,

Don

 

Good plan - anything that fails to show P1000/P1111 is simply not working and may well be failing to show other codes.

 

I have an older Innova 3130 and an iCarsoft 910 BMW version, and both often do not show the readiness monitor codes even though they show other DTCs perfectly well (in agreement with AutoEnginuity, my OTC scanner, SDD and other manufacturer-specific systems I have (HDS, Techstream, SPX, etc.), and Torque Pro/ELM327). It may have something to do with the age of their firmware and the various OBDII protocols now in use (ISO 9141, ISO 9141-2, ISO 14230 KWP2000, SAE J1850 PWM, SAE J1850 VPW, ISO 15765 CAN, etc.).

Cheers,

Don