Mass Air Flow Sensor Voltage

[Rebar 911]

I'm looking for help to check my limited knowledge of MAF Sensors and ECU's in my 2012 Land Rover LR4.

Issue: Between 40 - 50 mph (1600-2000 rpm) I experience some roughness; feels like lean air fuel ratio issue to diagnose.

Actions and Results:
1. I checked my GAP IID Tool for faults. None.
2. I cleaned the MAF sensors. No change.
3. I checked the MAF sensors diagnostics on my GAP IID Tool and found the voltage reading on MAF 1 is approximately 32V; I unplug the sensor and start the engine and the reading remains the same. MAF 2 goes between .7 and 2 depending on engine on/off/idle.

Assumption: Given that MAF 1 is being given a constant voltage of 32V (even when disconnected) and should range between 1 - 4v, I'm assuming I have an ECU issue?

If this is correct, any thoughts on a resolve are appreciated.

 

[jlglr4]

I’d check your mass air flow rates instead of voltage on the GAP tool and see what they look like - bank1 relative to bank2. I know they’re calculated from voltage, but I’ve had some strange things happen with the GAP tool - sometimes some functions don’t seem to work while others do. If the mass air flow rates are looking okay, I think you can just ignore the nonsense -30v reading.

The other thing to check is your fuel trims if you suspect a lean condition. Check both short and long, both banks, at idle, around 1500 , and around 2500 rpm (in park or neutral, just try to hold the throttle steady). Combine short and long, take note of whether they are positive (lean condition) or negative (rich condition), and how they change with increasing RPMs.

 

[Rebar 911]

I’d check your mass air flow rates instead of voltage on the GAP tool and see what they look like - bank1 relative to bank2. I know they’re calculated from voltage, but I’ve had some strange things happen with the GAP tool - sometimes some functions don’t seem to work while others do. If the mass air flow rates are looking okay, I think you can just ignore the nonsense -30v reading.

The other thing to check is your fuel trims if you suspect a lean condition. Check both short and long, both banks, at idle, around 1500 , and around 2500 rpm (in park or neutral, just try to hold the throttle steady). Combine short and long, take note of whether they are positive (lean condition) or negative (rich condition), and how they change with increasing RPMs.

Sharing the outputs here from idle to 1500 RPM to 2500 rpm. I follow what you're saying to look for but what do the results suggest?

 

[Rebar 911]

If I'm combining short and long term per bank at each idle cycle it suggests I'm typically running lean. So first off then, no issues with ECU or MAF sensor I assume? 2nd, would it be suggested to start smoke checking or do the numbers seem acceptable?

 

[Rebar 911]

Did the same test again (idle, 1500, 2500 rpm) after running the car for about 25 minutes. Results seem quite different.

 

[jlglr4]

Forgot to mention that the car needs to be warmed up. When its cold, it runs on a set fuel schedule. when its warm, it goes into closed loop feedback.

You are running a little rich on bank 2. I would next check your oxygen sensor voltages. you might have a bad o2 sensor.

 

[Rebar 911]

How would I know if they're were bad?

 

[jlglr4]

Been a while since I looked at this, so hopefully I explain correctly: There are 3 o2 sensors on each bank for this car: Pre-cat, mid-cat, and post-cat. The pre-cat sensor is used for fuel trim control, which should be sensor 1. See if you can find sensor voltage on the GAP tool for sensor 1, and then watch it or graph it using the graph button on the GAP tool - the voltage should move smoothly between about 0.1 and 0.9 v, back and forth like a wave.

I believe the mid and post-cat sensors are for emissions and cat converter health monitoring. I think only one of these two have a value on the GAP tool (sensor 2), and it stays pretty steady around 0.5-0.7v if I remember correctly.

 

[jlglr4]

Again - engine warmed up for this test.

 

[jlglr4]

The other thing I’ll mention - your fuel trims are off, but not way off. I’m not actually sure they’re off enough to cause any drivability issues. Still worth checking your o2 sensors, but I’m wondering if what you are feeling at 40 - 50 mph (1600-2000 rpm) is engine roughness (i.e., misfire) or some other vibration. Is it when you hold the throttle steady or when accelerating (or both)? Then it smooths out past that point? Does it do it both in sport mode and regular drive mode?