Mistake with multimeter now error code on 4R

I was about to use a multimeter to check which fuses had voltage with ignition on and off.

I didn’t pay attention and the probe on the multimeter was on the wrong port. It was in the 10A port (the one circled in the picture below).



As I touched the fuse with the red probe, there was a small spark.
I’m not entirely sure but I think it was the 4th fuse from the bottom left.




I then changed the port and checked all the fuses on the left side for voltage which all of them came back normal 12v. Also removed them but didn’t find any blown fuses.

However I have 3 error codes that cannot be removed. See below:

 

Any idea what's going on?

thanks in advance

 

@ElectroBoy would know better than me, but I think you grounded the circuit and may have burnt up some circuit boards and/or sensors.

The plug you used on the multimeter is to measure amperage, so it allows up to 10 amps to run through the multimeter circuit before its internal fuse pops. Either the internal fuse is rated a tiny bit higher than advertised, or it took longer to pop than the vehicle’s 10 amp fuse. Either way, it allowed too many amps to run through the vehicles circuit, and may have fried some boards.

Please take my reply with a grain of salt, I only have enough knowledge on this subject to be dangerous. Good luck.

 

What you are saying makes sense, unfortunately. I don’t know if there’s a way for me to check exactly what might be damaged or if there anything I can check to see if there’s an easy fix before I bring it to the dealership

 

the meter did the port amp lead then the meter is in the fuse ... also test all those fuses with the ohm meter take out the fuse and use the ohm meter .
then the magnifying tool to see if its a fuse ....

 

all the fuses that I tried on that side (bottom left) have continuity. Any idea which fuse might be the culprit for these error codes?

 

What was the black lead touching when the red lead sparked?

 

It was touching ground

also, I said a spark but in actuality it was more of a “flash” on the fuse right at the point where the red lead touched the fuse rather than a spark (don’t know if it’s different?)

 

@semprenissart, Check the 7.5A EFI No. 2 fuse as well. I put a yellow box around it. This fuse gets power from the 25A EFI NO. 1 fuse and supplies power to the MAF, Air injection control driver, Purge VSV, and Oxygen Sensors (Bank 1 Sensor 2, Bank 2 sensor 2). The ECM is not seeing power to any of these hence it is pretty unhappy. One of these is the likely culprit. I attached the relevant pages from the 2020 ECM Diagram.

Hope this helps. Let me know if the problem gets fixed.

 

@Old Red
The 7.5A fuse looks fine as well.

on a side note I disconnected the battery for 15 min to try resetting the code and see if they would leave.
The check engine light disappeared and I do not get the message “see dealer” on the dash anymore.
I drove around the block and it seemed like everything was normal.
However I used the obd scanner and it still shows the codes being in there as “permanent”.
If the issue is still there, would this be happening?
Or
Would the check engine light be back? Do permanent codes stay if everything is back to normal and need to be removed manually or are they supposed to go away once it’s actually fixed?

since all the fuses seem normal, I’m wondering if the “shock” created the codes to appear but in reality the truck is fine? Or does disconnecting the battery only removes the check engine light regardless of if there’s an issue or not?

 

Here’s the problem, the fuse has 2 sides, power in and power out. The setting you were in with the multi meter allows power to pass through to measure current. Your meter may have blown the fuse in it, but checking the cars fuses if you had it on the output side of the fuse you likely blew the fuse. If you had it on the power in side of the fuse, you grounded out the circuit while it’s not fused. You may have a can a worms on your hand.

 

@semprenissart, Ok good to know that fuse is ok. When you disconnected the battery it essentially cleared the memory of the ECU, but not the permanent DTCs. Hence why the MIL turned off and no more message.

Permanent DTCs are funny because they are meant to be "unclear-able" until the ECU logic determines that a fault no longer exists (Designed to keep people from cheating on emissions tests by just clearing the codes). If you drove it around the block and everything seemed ok (MIL off, no more message in the screen) I would just drive it for a day or two then recheck and try and clear the codes if they are still there. Take it up to highway speeds, run it for 30+ min, then recheck.

Permanent DTCs usually clear one of two ways

• After 3x consecutive confirmed fault-free monitoring cycles (i.e driving) (MIL off), the P-DTC is cleared at the start of the fourth fault free cycle OR,
• After one confirmed fault free monitoring cycle following a scan tool "clear DTC" request (already tried this right, so most likely bullet point above)

Driving Cycle aka "Fault free monitoring" (Can be any or combo of the below, my guess is bullets #2 & #3)

• OBD program must run and determine that the fault is no longer there (time unknown)
• Cumulative time since engine start is greater than 10min (Generic time, I don't know Toyota specifics)
• Vehicle operation >25mph for >5min
• Continuous operation at idle for >30sec

 

I’m guessing it was on the power side of the fuse since the fuse itself is not blown. So I most likely did ground out the circuit.

 

any risk of damaging the engine driving the 4R based on these codes? Assuming that there is actually something wrong with the MAF?

 

@semprenissart, @Old Red is the man on all things electrical, but I’ll offer a few ideas.

Since the MAF (P0102) is set and it is part of the emission control loop it probably needs a specific drive cycle to clear it. From what I recall doing it on a 3rd Gen it’s kind of complex and takes time. If you’re in a hurry to get this smogged you can research it to see how to execute it. Otherwise during normal driving you should stumble upon the sequence in a week or two.

When you checked the fuses did you take each one out of the circuit and check it for 0 ohms?

BTW, the internal fuse of the multimeter is surely blown. You won’t be able to make current measurements until it’s replaced.

Good luck, keep us informed.

 

Here are some examples of Toyota drives cycles to try.

https://axleaddict.com/auto-repair/Toyota-Drive-Cycle-Readiness-Monitors-for-Emissions

https://antiochstarsmogcheck.com/toyota-drive-cycle-obdii-readiness-monitors/

https://justsmogs.com/wp-content/uploads/2019/03/toyota-smog-check-drive-cycle-monitors.pdf

 

so I checked the fuses on the multimeter. There are 2 fuses, one 10A and one 500mA.
only the 10A fuse was blown. Went to ace hardware and got a new one. Re-tested the fuses in the fuse box of the truck and they all come back 0 ohms.

Also I drove about 10 miles and checked for codes again.
Now there’s only 1 code left out of the 3!
It is P0102 that’s left. I do not need to get the truck smogged so there’s no hurry on this end.
Maybe I need to drive more for the last one to clear?

A big thank you to everyone in this thread for the massive support so far!

I’m going to read the links you provided above this post and will keep you guys updated if I see the last code disappear.

 

yes you changed the multi meter in the fuse in the morning ...

 

look up the MAF ... the p0102 code is a MAF spray cleaner ...also the wiring of the connectors and wires .........take the MAF out then maf cleaner see if it works ..

 

I checked the connections and the wires this morning. They looked fine. I have not taken the MAF out since i didn’t have any issue up until now and the truck is not even 1 year old. So I figured it shouldn’t need to be cleaned…
But I’ll get some MAF cleaner tomorrow and see if that helps

 

There's no reason to clean the MAF on a vehicle less than one year old, or the connector. From what the OP stated, the vehicle drives just fine. This is an ECU logic issue due to lack of fused power on a certain circuit leading to P-DTC that needs to be cleared with driving. Disconnecting the MAF may just set more codes. I wouldn't waste the time pulling the MAF. If it's not broken, don't fix it as the old adage goes.

 

Yes it’s probably wise to leave it alone if it’s not needed.
the less I touch the better it is

 

What exactly spurred this project?

It certainly demonstrates the vulnerability of a modern cars electrical system.

 

It seems he was mapping out the fuse functions (always On 12V, Accessory On 12V, Ignition On 12V) for a future project. This is good to know because there usually are spare locations that have voltage available but no load is connected. So it’s a convenient place to plug in a fuse tap.

His mistake (which many a technician has done) was to connect his meter leads wrong so he essentially touched the battery 12V to ground through the meter. The meter’s current fuse blew and saved the day. But that instantaneous power surge to ground probably was enough to partially reset some memory locations in an ECU. Good electrical design practices anticipate these things and provide some circuit protection, but not always, and everyone should be very careful when working on the electrical system. It’s too easy to defeat one of the many ECUs in modern cars.

 

Thanks for explaining.

 

the code 102 is the MAF to clean it ..now the new runner is 1 yr old and if someone sprays the oil in the air filter or other chemicals ..

 

The code says MAF circuit low which could be a dirty MAF among other things as far as I understand. However that code showed up because of what i accidentally did with the multimeter. Not because the MAF is dirty.

So far it seems like I just need to keep driving the truck for the code to disappear (hopefully)
I am not getting a rough or weird idle. Engine doesn’t stall. It doesn’t look like it’s running lean or rich. Getting normal mpg. Normal acceleration. Goes in the whole rpm range when I floor it.
So it seems to me like the MAF is physically okay so far

 

the MAF p0102 code is dirty / or the electronic components in the MAF sensor with the spike voltage ..
my GM 15 yrs old the MAF is the p0102 code and a rough idle ...install it new, is the idle changed it new and the code is off and the idle is very good..

 

UPDATE:

Everything is back to normal! No more codes no engine light no limp mode.

It took about 195 miles for P0102 to clear.
But like you guys said, rather than the mileage it has to go through a specific set of drive cycles. I just drove normally, I did not try to go through all the weird sequences. The one that took the longest for me was that some of these had to be while the tank is 1/4 to 3/4 full and with my not so great luck, I had refilled to the brim right before I messed with the multimeter.

All in all it feels great to be worry free once more.

A special thanks to @Old Red , @ElectroBoy , @Agent_Outside for troubleshooting and all the others as well for their help/input

 

Great! Now don’t touch anything electrical.