MY 98 D1 4.0 seems to run OK (with the occasional P1314 code thrown) so my MAF must be functioning, but UltraGage reports MAF values of 0.10 at idle and 0.17 at 2000 RPM; The UG manual says the range should be 0 to 665 and the MPG it reports is off the chart.

I found this in the archives.

"Mass air flow sensor (MAF Sensor)
The "hot wire" type mass air flow sensor is mounted rigidly to the air filter and connected by flexible hose to the plenum chamber inlet. The sensing element of the MAF Sensor is a hot wire anenometer consisting of two wires, a sensing wire which is heated and a compensating wire which is not heated. Air flows across the wires cooling the heated one, changing its resistance. The ECM measures this change in resistance and calculates the amount of air flowing into the engine. As there is no default strategy, failure will result in the engine starting, and dying when it reaches 550 rev/min, when the ECM detects no MAF Sensor signal. The fault is indicated by illumination of the malfunction indicator light (MIL) on North American specification vehicles."


I can't find any MAF test specs in the Rave. Can anyone tell me how to test it? Such as what wires and what the range of resistance it should exhibit at what RPM? Should I try cleaning it with contact cleaner or carb cleaner or brake cleaner or something else? I am used to seeing a MAF with a flap on my 80s vintage Jaguars; this heated wire concept is new to me.

 

UltraGage support said, "Its more likely that the MAF is good and that the ECU is not providing the output correctly. However, there is another possibility." And They asked me to run the UG "factory test" and send them a photo of the results.

Hoping I don't have to dig into the MAF just yet, as I try to subscribe to the twin philosophies of "First, do no harm" and "If it ain't broke, don't fix it."

 

I tried to find an answer to this as well the other day. So I could test the two spares I have in the garage. But was not able to find a straight and simple answer. There were some TSB's on another forum that gave specific test but they were a bit outside of my shade tree mechanics tool kit. I also read that you can check the voltage on the wire that runs to the ECU at different RPM's and that will tell you if it's within range.

I finally decided to just try and test the resistance across the three pins(1-3, 1-2 and 2-3) for each of the 3 MAF's I have including the one currently working in my truck. They were all roughly within the same range so I'm just going to assume they all work.

 

Yeah all of mine display approx the same reading on the ug

If it is the ug telling me wrong but ecm and MAF are working correct that's fine with me

 

What readings are you seeing, Tom? Mine are all below 1 so far.

I sent this to UG:
I just went for a short low speed drive down to check on the boat house and the MAF 1 and 2 values ranged from .07 at idle to .55 coming back up the hill so there is a range being reported, but far below the 0 to 655 range listed in the UG manual. I am guessing from your replies that the difference in MAF values is too great for the MPG to be corrected with calibration? I have yet to find any resistance specs for the MAF to check its operation; is there a chance the ECU (or ECM as LR calls it) is reporting actual resistance values rather than g/s?

And they replied:
The output for MAF violates the OBDII standard. As such, there must be a defect somewhere, either in the MAF or in the ECU. We suspect the ECU. Try the calibration. Best regards, UltraGauge Support

They has previously said:
Some ECUs scale the MAF output. However, based on the factory test results, your ECU does not, or atleast the ECU is not reporting that it is scaling the output. If the ECU is scaling the output, running the Fuel calibration will solve the issue. However, as we have never heard this issue from any other Discovery owner....we suspect there is an issue with your vehicle. Check with the service department of your local dealership to see if there is a general firmware update available for your vehicle. In general dealers are resistant to helping when there is nothing in it for them. So it is generally best to speak in terms of getting the update just to make sure you have any safety and emissions updates.
Alternatively, check with a Discovery specific forum to see if others have had this issue with the MAF output. Best regards, UltraGauge Support



Tom, If your UG MAF values are in the same range as mine, I will assume the ECM is working as Land Rover intended and will ask if there is a different protocol than the 9141 that might work better.

 

Do you have the link to the test info, Buddy?

 

phil my ug is the 9141 on boot and I have the same maf readings as you, like I said if the ecm is reading the maf correct so the air fuel is correct in the engine but displays bad on the ug no biggie, but there is a chance the maf is being read incorrect which can be an issue


since I did the fuel pressure regulator and injector upgrade I have had no codes and it runs normal/ smooth

 

Thanks, Tom.

UG had said earlier "... as we have never heard this issue from any other Discovery owner we suspect there is an issue with your vehicle."

but now we know it is not just my specific ECM reporting these values and I sent that info to the UG support team and asked if there is a way to tell it to scale the MAF values by 1000.

Is anyone with other year D1s getting similar UG MAF 1 or MAF 2 values? Or D2 owners? Is anyone getting accurate MPG or DTE values from a UG? If so, let us know the year(s).

Perhaps there was a change in the ECM along the way, or perhaps there is a firmware update (as UG suggested) that changes the way MAF is reported to the OBDII system. If not, and no one has reported it before, I'll suggest they need to update their exceptions page on the UG web site to let other Rover/Disco owners know the limitations before they buy.

If it is a Land Rover ECM reporting problem I'd expect other productss like ScanGage to have the similar off-the-chart results, assuming they report MPG or DTE.

 

Here's UG's latest reply:

Your vehicle only supports 9141. The protocol is only the transport. The data transported will be the same regardless of protocol.

1. Perform the Fuel Cal
2. Look for an Firmware update.

Best regards, UltraGauge Support

I emailed the nearest LR dealer in Little Rock:

Hi Folks,
I have a 1998 Discovery 1 VIN SALJY1248WA756092 and I have two questions. 1. Are there any outsdanding recalls for this vehicle that have not been performed?
2. Are there any firmware updates that would affect the MAF values reported by the ECM to the OBDII system? The reason for the second question is that UltraGage says that the MAF values reported by my ECM do not meet the OBDII standards and do not report any scaling to be used. Values reported are 0.07 to 0.55 and The UltraGage expects 0 to 655.

Thank you for the previous help in determining the code for my radio which worked a treat.

 

Sorry, I didn't save the link since it was not helpful and their numbers were off from mine by a factor of over 1,000. So I just compare compare the three I have including the one on my truck.