MAF sensor woes

[atalarico]

Hey all,

Last week after getting back from a 6 hour drive, I was sitting in the car wash and the 4runner just died. It wouldn't start the first time I tried, and then it did. CEL and then VCS trac lights came on.

Got home and pulled codes and got:

============1==============
P0102
Raw code: 0102
ECU: 10
Status: Confirmed
OBDII: Mass air flow (MAF) sensor/volume air flow (VAF) sensor - low input
Toyota: Mass or Volume Air Flow Meter Circuit Low Input
============2==============
P0101
Raw code: 0101
ECU: 10
Status: Confirmed
OBDII: Mass air flow (MAF) sensor/volume air flow (VAF) sensor - range/performance problem
Toyota: Mass or Volume Air Flow Meter Circuit Range / Performance

Pulled the MAF sensor and cleaned it using the special spray. No dice. Cleaned the throttle body. No dice.

Ordered a new OEM MAF sensor and just got it today (after waiting 5 days for it to arrive). Threw it in, and tried clearing the codes. No change.

The truck is stuck in limp mode (won't go above 3,000RPM), and every time I clear the codes the truck dies again. It's driveable under 65 otherwise, as it just takes two times to start, no more, no less.

What the heck is going on!? Do I need to reset the ECU again? I'm writing this as the battery is sitting disconnected, so I'm going to head out there after I submit this and try it all again. So bummed.

 

[atalarico]

Bump? No ones had MAF issues like this?

 

[BackOff]

Cloged up air filter?
Sound like something got wet in the carwash?

 

[atalarico]

Cloged up air filter?
Sound like something got wet in the carwash?

Yeah I tore everything apart from the air filter box onward to the throttle body. Nothing is off.

I’m kind of wondering if the wire harness got messed up but I don’t know how to check that with an ohm meter.

 

[4RunnerAquasport]

Any past rodent issues? Could the ECU connection have gotten wet? Just reaching here, but maybe a crazy idea will give you one. Definitely curious. I hope you get it sorted out soon.

 

[atalarico]

Any past rodent issues? Could the ECU connection have gotten wet? Just reaching here, but maybe a crazy idea will give you one. Definitely curious. I hope you get it sorted out soon.

Nah nothing to speak of. It happened in a car wash so I’m guessing something got wet that wasn’t supposed to?

 

[4RunnerAquasport]

The new MAF is a dealer OEM? or online purchase? I keep hearing stories of counterfeit parts online. Hope it's something simple and not too aggravating.

 

[atalarico]

The new MAF is a dealer OEM? or online purchase? I keep hearing stories of counterfeit parts online. Hope it's something simple and not too aggravating.

It’s dealer OEM. Sigh. So lost. I hate to admit defeat but it’s going to the shop.

 

[08TxRunner]

Take a few minutes and look for a very large vacuum leak. When unmetered air gets into the engine it can throw a MAF code.

 

[atalarico]

Take a few minutes and look for a very large vacuum leak. When unmetered air gets into the engine it can throw a MAF code.

Yeah, I checked and didn't see anything.

I pulled a couple more codes after driving it for a bit related to the O2 sensor:

P0051
Raw code: 0051
ECU: 10
Status: Confirmed
OBDII: Heated oxygen sensor (HO2S) 1, bank 2, heater control - circuit low
Toyota: Oxygen Sensor Heater (Bank 2 Sensor 1) Circuit Low
============4==============
P0031
Raw code: 0031
ECU: 10
Status: Confirmed
OBDII: Heated oxygen sensor (HO2S) 1, bank 1, heater control - circuit low
Toyota: Oxygen Sensor Heater Circuit Low Input (Bank 1, Sensor 1)

Part of me thinks (hopes) that's just a symptom of whatever is throwing the MAF off. Anyway, I dropped it off at the shop since I'm at a loss, so we'll see.

Sigh.

 

[08TxRunner]

How did you check? Just looked around the engine compartment? If so that's not going to do it.

 

[atalarico]

How did you check? Just looked around the engine compartment? If so that's not going to do it.

I mean, I don't have a vacuum gauge pump, but I checked all of the vacuum hoses for obvious signs of breakage, etc., and used the carb cleaner trick around the usual suspects and listened for the engine idle change.

I didn't check my headers though, and I wouldn't be surprised if there was a shoddy weld on the DT headers that gave out.

We'll see what the shop says since they likely have smoke machine. I'm sure it is a vacuum leak somewhere, just curious where since it's beyond my abilities at this point.

 

[atalarico]

My go-to shop couldn't fix it. He thinks it's something going on with the computer. Showed me a print out of the MAF airflow rate is just flatlined at .23 g/s whether it's being given throttle or not. He tried swapping another MAF but same results. He didn't see any vacuum leaks either. He said replacing the computer might be the fix, but he can't do that since he doesn't have a way of programming it. That sounds expensive as hell.

Dealership doesn't have openings until the 16th, so I'm taking it to another place in the mean-time to see what they think.

FML.

 

[4RunnerAquasport]

[MENTION=55192]atalarico[/MENTION] Check this guy out from NZ. He is a little hard to understand but knows the UZ platform better than anyone. He just went through the wire loom on a 2UZ in this video. He might be able to shed some light, because he is an expert at ECU swaps. One thing I hear is the security key code is a stumbling block for this. Not sure it affects the older UZs like ours. He shares a wealth of knowledge and there may be something in his videos that might help and he is good at responding to comments in his vids. Good Luck!!
CartuneNZ You Tube

 

[waypoint]

Check your fuses, especially the ones labeled EFI 1 and EFI 2, and A/F Heater. Because this problem onset after a car wash, it's possible water got into a connector and shorted a power circuit to ground.

And by check them, I mean physically remove them and examine the fusible element, then probe them with a meter to verify continuity (infinity resistance reading).

If there's any doubt that each fuse is good, replace it.

If the problem continues, disconnect your battery negative and then remove & inspect each connector on the ECM. Look for corrosion, moisture, bent pins. Spray out the connectors with electrical parts cleaner, let dry, then reassemble.

 

[atalarico]

Check your fuses, especially the ones labeled EFI 1 and EFI 2, and A/F Heater. Because this problem onset after a car wash, it's possible water got into a connector and shorted a power circuit to ground.

And by check them, I mean physically remove them and examine the fusible element, then probe them with a meter to verify continuity (infinity resistance reading).

If there's any doubt that each fuse is good, replace it.

If the problem continues, disconnect your battery negative and then remove & inspect each connector on the ECM. Look for corrosion, moisture, bent pins. Spray out the connectors with electrical parts cleaner, let dry, then reassemble.

You were close! Just heard from shop #2 that it was the O2 sensor harness got fried by my exhaust, which was shorting out the EFI circuit. They're re-wiring the harness and then securing it away from the exhaust.

Hot dang!

 

[4RunnerAquasport]

You were close! Just heard from shop #2 that it was the O2 sensor harness got fried by my exhaust, which was shorting out the EFI circuit. They're re-wiring the harness and then securing it away from the exhaust.

Hot dang!

This car wash have heavy side or undercarriage jets or was this just a coincidence that it went out after the wash?
I wonder if it had already suffered damage and the wash just exposed the short?
Lol I'm sure you don't care at this point, but it's good to document this type of bs for the forums sake. Glad to hear it! [MENTION=172281]waypoint[/MENTION] Good Stuff!

 

[atalarico]

This car wash have heavy side or undercarriage jets or was this just a coincidence that it went out after the wash?
I wonder if it had already suffered damage and the wash just exposed the short?
Lol I'm sure you don't care at this point, but it's good to document this type of bs for the forums sake. Glad to hear it! [MENTION=172281]waypoint[/MENTION] Good Stuff!

The undercarriage jets are the reason I go to that wash lol

Here's my educated guess; a couple months ago, the metal heat shield that goes around the driver's side catalytic converter that's on the exhaust manifold fell off (Exhaust shield hitting my driveshaft!). I looked at it and it was shoddily cut at the top from the shop that installed my DT headers to the point where there was only one small part of metal keeping it on.

Anyway, it was rattling like heck and hitting my drive shaft, so I had to pull it since I didn't have a way of securing it back to the cat. My guess is that somewhere in that process or because of that, the heat shielding on the O2 sensor was damaged. I had just taken the truck on a 6 hour drive down to Ouray, off-roaded it for a week, and came back. It was a long and hot drive back...

I'm getting it back tomorrow so I'm going to ask which side it was, and if it was driver's side then it'll make a lot more sense.

I'm just really glad it wasn't a bad ECU since shop #1 said it could be that but they didn't have the equipment to reprogram that stuff (which is funny because it's just Techstream, and I have that on a laptop).

 

[4RunnerAquasport]

The undercarriage jets are the reason I go to that wash lol

Here's my educated guess; a couple months ago, the metal heat shield that goes around the driver's side catalytic converter that's on the exhaust manifold fell off (Exhaust shield hitting my driveshaft!). I looked at it and it was shoddily cut at the top from the shop that installed my DT headers to the point where there was only one small part of metal keeping it on.

Anyway, it was rattling like heck and hitting my drive shaft, so I had to pull it since I didn't have a way of securing it back to the cat. My guess is that somewhere in that process or because of that, the heat shielding on the O2 sensor was damaged. I had just taken the truck on a 6 hour drive down to Ouray, off-roaded it for a week, and came back. It was a long and hot drive back...

I'm getting it back tomorrow so I'm going to ask which side it was, and if it was driver's side then it'll make a lot more sense.

I'm just really glad it wasn't a bad ECU since shop #1 said it could be that but they didn't have the equipment to reprogram that stuff (which is funny because it's just Techstream, and I have that on a laptop).

Wow, that could have been a DEEP rabitt hole. I missed your post about the o2 sensors and didn't remember you had the header install, I was headed the wrong way too lol. Sorry about that.
New ECU? That woulda SUCKED! Just glad your making progress!

What OS you have running the techstream? I haven't jumped into that pool yet, relying mostly on the forum and Torque Pro app for diagnosis and live data on my 4th and 5th gens. I need a new distraction with all the crap going and unemployment to boot.

 

[atalarico]

Wow, that could have been a DEEP rabitt hole. I missed your post about the o2 sensors and didn't remember you had the header install, I was headed the wrong way too lol. Sorry about that.
New ECU? That woulda SUCKED! Just glad your making progress!

What OS you have running the techstream? I haven't jumped into that pool yet, relying mostly on the forum and Torque Pro app for diagnosis and live data on my 4th and 5th gens. I need a new distraction with all the crap going and unemployment to boot.

No worries at all! I clearly had no idea.

I got Techstream in some bundle package with a cable on Amazon I think. I have it running on an XP VM which is pretty funny considering how old it is. It’s actually a VM running on a Bootcamp Windows 10 on a Mac laptop. So a VM on a VM.

It’s super useful though, and it saved me a boatload when I reset my Immobilizer and programmed new master keys since the car only came with a valet.

You’ll have fun with it!