Supercharged Sports that suddenly stop charging

A few weeks ago, I had a strange and curious experience with a Range Rover. It started with a simple warning light, and the usual request. “Can you reset my check engine light so I can get a sticker?”

Why do so many people think these lights come on just so they can be reset?

What possible purpose would that serve?

I explained that we’d have see what fault codes were stored, at which time we could decide what to do about them. In most cases, when you see a check engine light, you need a repair, not a reset. Codes mean many different things. Sometimes, they point to specific repairs. For example, a “replace Thelman wire” code is self-explanatory. You replace the Thelman wire. Other times, codes are more vague. “Fuel mixture out of range” can mean most anything, from air leaks to snoot problems.

This particular car had a code for inoperative cam adjusters, which was strange, because Supercharged Sports don’t have cam adjusters at all. We cleared it, and it came back right away. We looked closer at the engine, to make sure it had not grown cam adjusters on its own. It hadn’t.

Every now and then, mechanics run into situations like these . . . codes that don’t make any sense at all, yet will not go away. When that happens here, we look to see if a software update will fix the car. We use our test system to get the software version and we compare that to the latest version Land Rover lists for that particular vehicle. If there’s newer software, we install it. When we tried that, we found something even stranger.

The vehicle had software for a non-supercharged Sport installed, and the computer was telling us it had never been re-programmed. Either the car had been running around for four years with wrong software, or the computer was lying. Which was it?

After some interrogation of the motorist associated with this particular vehicle, we concluded that the software was probably original. How they made it through four years of operation, only complaining about a check engine lamp now, remained a mystery.

We downloaded new and correct software, and the problem vanished. The cam adjuster faults disappeared, and all tests were normal. We felt great pride in a job well done, and handed the vehicle back to its owner. Unfortunately, this particular Sport did not stay fixed.

“My car was in the passing lane, doing 70, when it lost all power and the check engine light came on. I coasted to a stop, shut it off, and started it again, and it was normal. That’s happened every time I drive to New Haven, and I’m getting scared to take my truck on the highway. What’s up?”

Did the car have an aversion to New Haven? I’ve seen such things before. “Bring it in,” I said, and we’ll see what the codes tell us. A check revealed a P2601 code, which points to a failure of the pump that moves water through the supercharger when you get on the throttle. His seemed to be failing. But why now?

A check of Land Rover service bulletins held the answer:

Land Rover Technical Service Bulletin #LTB00041, Rev 2

Reduced Power Under Load

Possible DTC P0096 and/or P2601 Stored

AFFECTED VEHICLE RANGE:

Range Rover (LM) Supercharged 6A198058 to 7A261419

Range Rover Sport (LS) Supercharged 6A901924 to 7A109767

CONDITION SUMMARY:

REDUCED POWER OR MISFIRE AT HIGH ENGINE LOADS

Situation: The customer may complain of reduced power and or a misfire at high engine loads and road speeds, with the possibility of Diagnostic Trouble Codes (DTC) P0096 and/or P2601 stored. The electrical harness power supply and ground for the auxiliary coolant pump may be cross connected in connector C3006. The pump will run backwards causing the Engine Control Module (ECM) to reduce power to prevent damage because the pump flow is low. The auxiliary coolant pump will be degraded under these conditions.

Action: Should a customer express concern, modify the wiring at connector C3006 to the correct positions and install a new supercharger coolant pump as part of the repair if either the fault codes or the incorrect wiring is discovered following the Repair Procedure outlined below.

We checked, and this fellow’s car did indeed have the reversed wiring. A swap of the wires and a new pump, and he was on his way.

How does this situation come to pass? I spoke to Tony Gill, who heads Land Rover tech support at Autologic in the UK. He suggested a few possible answers.

This car seemed to have the wrong software put in at the factory, As a result, it may have never tried to use the auxiliary pump because the engine controller didn’t know it was there. Non-supercharged Rovers don’t have this pump. Of course, that does not explain how this truck went four years looking for cam adjusters that were never there . . .

It’s also possible that the pump was strong enough to push coolant through the supercharger backwards, against the flow of the regular water pump. It may have done that for all this time, and finally decided to fail.

We may never know the full answer, but it does appear to be fixed.

The moral of this story . . . check your software. Even in new vehicles, mistakes happen. And some of them take a long time to find. It’s shocking to me that there are four-year-old vehicles out there with wiring that was backwards from Day One, but it’s indisputably true.

That is the wonder and magic of British Motorcars.