Restricted Performance and GAP IIDTool Faults

[StewG]

A month ago, I got the dreaded Restricted Performance fault up on the dash display. It seemed a good idea to get a GAP IIDTool to help me to find out the cause before I spent hard-earned $$$ on repairs. I bought the tool, it has been delivered and activated and now I don't know what it all means. After clearing all faults, the following fault reappeared:

U1A24-87 (28) MOST ring complete, no communication - Bus signal/message failure - missing a message.
At 202656 km Triggered on 14-11-2021

This sounds to me like a loose wire or bad electrical connection. Any ideas of where to start looking would be appreciated.

[Tombie]

MOST bus is the audio system

[StewG]

Ok, so the MOST is associated with the audio system. From what I have read in the GAP Tool manual, U faults are generally able to be cleared and ignored unless persistent. I've still got the restricted performance and red warning light up on the dash display, but no other ECU faults. That seems to be illogical to me.

175670

[Macadamia]

in the the advanced settings of the faults - add in pending faults and see what pops up.

[StewG]

OK. So Christmas has intervened in my diagnostic efforts. My D4 battery was getting low so I charged it up and noted that the Restricted Performance and RED waring light was still up with ignition on.
Now the GAP Tool was telling me:

PCM - Engine Diesel 3.0 L HSCAN - 1 fault

P010D-00 (AF) Mass or volume air flow B-circuit high
At 202656 14-12-2021

So I thought that if I swapped the MAF sensors and the fault goes to A then it is a faulty B sensor. Easy. Not so easy... With a bit of fiddling with the looms, I managed to swap the connectors. I noticed that the forward sensor incorporated a temperature sensor. So any fault there could be ignored.

After swapping the sensor connectors, started the engine and got No Faults on the GAP Tool. So I swapped the connectors back and went for a drive around the block (about 5 minutes). The Restricted Performance was no longer showing, but the Red Warning indicator was still on and the engine felt sluggish (like no turbos).

I remembered to re-read this thread and on the GAP went for Advanced faults pending and got the following:

PCM - Engine Diesel 3.0 L

P010B-22 (64) Mass or volume air flow B circuit - range/performance - General Signal failure - signal amplitude&gt: maximum
At 202659 km
Triggered on 09-01-2022 14:47:26

P010D-00 (27) Mass or volume air flow B - circuit high
At 202659 km
Triggered on 09-01-2022 13:44:34

I can't see any oil escaping from the engine, so it is unlikely to be a manifold (the RH manifold was replaced not long ago). Can it be a faulty MAF sensor or is there more investigating to be done?

[DiscoJeffster]

OK. So Christmas has intervened in my diagnostic efforts. My D4 battery was getting low so I charged it up and noted that the Restricted Performance and RED waring light was still up with ignition on.
Now the GAP Tool was telling me:

PCM - Engine Diesel 3.0 L HSCAN - 1 fault

P010D-00 (AF) Mass or volume air flow B-circuit high
At 202656 14-12-2021

So I thought that if I swapped the MAF sensors and the fault goes to A then it is a faulty B sensor. Easy. Not so easy... With a bit of fiddling with the looms, I managed to swap the connectors. I noticed that the forward sensor incorporated a temperature sensor. So any fault there could be ignored.

After swapping the sensor connectors, started the engine and got No Faults on the GAP Tool. So I swapped the connectors back and went for a drive around the block (about 5 minutes). The Restricted Performance was no longer showing, but the Red Warning indicator was still on and the engine felt sluggish (like no turbos).

I remembered to re-read this thread and on the GAP went for Advanced faults pending and got the following:

PCM - Engine Diesel 3.0 L

P010B-22 (64) Mass or volume air flow B circuit - range/performance - General Signal failure - signal amplitude&gt: maximum
At 202659 km
Triggered on 09-01-2022 14:47:26

P010D-00 (27) Mass or volume air flow B - circuit high
At 202659 km
Triggered on 09-01-2022 13:44:34

I can't see any oil escaping from the engine, so it is unlikely to be a manifold (the RH manifold was replaced not long ago). Can it be a faulty MAF sensor or is there more investigating to be done?

Have you enabled Pending Faults under advanced? I would expect to see a P006a fault with that which is a volumetric mismatch between MAF and MAP. I say this based on you swapping the MAF and still it says the B sensor. I had this two, I swapped MAF, was still there, then found the pending fault. It was an intake leak.

[StewG]

Have you enabled Pending Faults under advanced? I would expect to see a P006a fault with that which is a volumetric mismatch between MAF and MAP. I say this based on you swapping the MAF and still it says the B sensor. I had this two, I swapped MAF, was still there, then found the pending fault. It was an intake leak.

I did enable the Advanced > Pending faults, but I had already swapped the sensors back. I'm going to have to do the whole exercise again to see if B fault changes to A fault. [bigsad]

Apart from two trips around the block, I've barely driven the car in many months and both the D4 and my caravan are a spiders' paradise - covered in cobwebs...

[DiscoJeffster]

I did enable the Advanced > Pending faults, but I had already swapped the sensors back. I'm going to have to do the whole exercise again to see if B fault changes to A fault. [bigsad]

Apart from two trips around the block, I've barely driven the car in many months and both the D4 and my caravan are a spiders' paradise - covered in cobwebs...

It may be the MAF then. Swap them, then see if the fault goes until the second turbo kicks in. After that, if confirmed, try a MAF cleaner before you buy a new one.

[StewG]

Over the past few days, I have been fiddling with the MAF sensors, including cleaning with CRC MAF Sensor Cleaner (it made no difference). The attached pdf (if I get it attached ) shows GAP Tool screen shots and explanations. I'm still at a loss to know exactly what the problem is although I have seen a small amount of oil on the LH intake manifold and hope that it is not cracked. The RH side was replaced about two years ago when I first got "Restricted Performance" and that set me back about $1600. [bigsad]

[DiscoJeffster]

Over the past few days, I have been fiddling with the MAF sensors, including cleaning with CRC MAF Sensor Cleaner (it made no difference). The attached pdf (if I get it attached ) shows GAP Tool screen shots and explanations. I'm still at a loss to know exactly what the problem is although I have seen a small amount of oil on the LH intake manifold and hope that it is not cracked. The RH side was replaced about two years ago when I first got "Restricted Performance" and that set me back about $1600. [bigsad]

Put a piece of white paper on top of the manifold and put the cover back on. Go for a drive, nail it, then check for soot on the paper. Easy test. Do the same on top of the throttle body/y piece. Mine split there too.

[StewG]

Put a piece of white paper on top of the manifold and put the cover back on. Go for a drive, nail it, then check for soot on the paper. Easy test. Do the same on top of the throttle body/y piece. Mine split there too.

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.

176323

[DiscoJeffster]

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.

176323

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.

[Eric SDV6SE]

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.

[StewG]

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.176450176451

[StewG]

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!

[DiscoJeffster]

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.

[BradC]

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

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

[StewG]

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).... [bigsmile1]

[StewG]

Just an update: The D4 has been used now and then since MAF Air Flow Sensor was replaced with no trouble at all. Full of confidence, The caravan was hitched up for a five day trip to Wilson's Promontory. Halfway there, the dreaded Restricted Performance popped up again! So we limped into Tidal River and camped for the week. Checked the faults with the GAP Tool and this time it was "P006A-00 (EC) Manifold absolute pressure - mass or volume air flow correlation". Whipped off the engine 'lid' and saw a quantity of oil on the LH intake manifold. [bigsad] Limped home again and that is that. The RH inlet manifold was replaced three years ago and it seems that it is the LH's turn now. I'll give a further update when I feel up to looking at the problem.