Thread: Restricted Performance and GAP IIDTool Faults

Originally Posted by StewG

Two pieces of paper and a drive around the (extended) block for about five minutes. No visible soot or oil. But while I had the cover off, I removed, cleaned with CRC MAF Sensor Cleaner and refitted the sensor that sits on the Y-piece. I'm only getting the one fault now as shown below.

Screenshot 2022-01-14 184437.jpg

That’s the Manifold Absolute Pressure sensor (MAP) and is used as a comparison to the MAF expected flow. If there’s a discrepancy between the two there is generally a leak somewhere in the system.

MAF sensor is just after the airbox. 1 off on the 2.7 and 2 off on the 3.0l clean them with contact cleaner or sensor cleaner.

I tried the clean white paper trick again. One piece over RH intake manifold, one over LH manifold and one over the Y-piece and went for a longer drive; about ten minutes. All paper was clean, so I don't see that there are obvious leaks. I also gave the MAF sensors another dose of CRC MAF Sensor Cleaner.

I measured the voltages on the MAF connectors with respect to chassis ground, first with Power on only (Power) and then with engine running at idle (Run) and also with revs at 2,000 rpm (Fast). The four pins on each connector run from 1 (inboard) to 4 (outboard). Pin 2 is for the temperature sensor on front MAF only.
The results are:

Pin 1 Front Power 2.7V, Run 2.7V, Fast 2.7V - No change.
Pin 1 Rear Power 2.9V, Run 2.9V, Fast 3.6V - change at revs.
Pin 3 Front and Rear 0.02V - No change - assume 0V.
Pin 4 Front and Rear Power 12.6V, Run/Fast 14.3V - assume nominal 12V (Battery voltage).

From the above result I'm 80% sure that I need a new replacement MAF for the front position. Comments are welcome.PXL_20220115_040050841_cr.jpgPXL_20220120_055520377_cr.jpg

Just to give an update. I received a pair of new MAF Sensors direct from the UK today. Put one in place of the front unit and cleared all faults. "Restricted Performance" has now vanished. A trip around the block with plenty of throttle made the D4 leap - thanks to the turbos - and I couldn't be more relieved at the fix. I'm now going to wash the car to celebrate.

Thanks to all the posters past and present that helped me to track down the eventual problem and how to fix it. Without this forum I would have had to go to a stealer or indy to get it fixed.

Like someone says: Land Rover - turning owners into mechanics!

Fingers crossed. In your post, you mention no change on one MAF as the source of a problem. The reason only one MAF is active and values changing by revs is because below 2500rpm the second turbo is isolated - which draws through the other MAF. It is normal for one MAF only to be active in your test scenario.

I hope your problem is solved. Give it a few weeks.

Originally Posted by StewG

Like someone says: Land Rover - turning owners into mechanics!

I think these days it's more like training diagnosticians.

Originally Posted by DiscoJeffster

I hope your problem is solved. Give it a few weeks.

I also hope the problem is solved. I'm happy if I get the right result from the wrong diagnosis. I still have a spare MAF sensor (or two)....