Possible electrical issue or bad sensor?

So a little while ago I posted a thread about an intermittent crank/no start issue with my 2013 base model access cab. While that problem still persists, it's less common since it's been colder lately.

I've noticed if I drive to work on a cold morning, then try to start my truck in the afternoon if it's significantly warmer out, it takes some finagling to get the truck to start. For this issue, I've been told to look into the crankshaft position sensor. Nothing ever went wrong once the truck was running.

Recently, however, I've run into another more worrisome issue, and I'm not sure if it's related. Every once in awhile, the tachometer and the temp gauge will both drop to zero, the airbag light will come on, and, if I'm driving, the traction control light will start flashing. The engine doesn't shut off, but the gas pedal does nothing. This will happen for about ten seconds before everything goes back to normal, and the engine will stumble a bit, like a misfire. My power steering and brakes will still work normally, but because of the gas pedal not working I have to pull over to the side of the road until the issue fixes itself.

Now just a few weeks ago, I installed bigger tires (235/75/R15 over stock 215/70/R15) and had the shop balance them and perform an alignment for me. The airbag light/tachometer issue didn't pop up until about a week later, but I'm not fully convinced it has anything to do with that.

My question is, can a bad/failing crankshaft position sensor cause any of these symptoms? Are there any other potential causes I should look into? Does the tachometer/temp/airbag/traction control issue sound like it could be related to the initial crank/no start issue?

I'm not a mechanic by any means; I do my own oil changes, mount my own tires, and can use my tools as needed when I know what needs to be fixed, but diagnostics are not my strong suit. I'm pretty good with electronics but I can't see how any of the symptoms are related.

No check engine light, no codes, no blown fuses, I'm at a loss for what might be going on. Everything runs fine the majority of the time.

 

There's a remote chance that it is a battery related issue. I would start by cleaning and tightened the battery terminals. Make sure they are sparkling clean. How old is the battery?

 

I actually just replaced the battery within the last two months. All the terminals are clean

 

Mouse inspection is where I would start..

 

Check the grounds and clean electrical connections.

 

I believe a bad crank sensor CAN be the problem. They do go intermittent at times as far as I know. Are you sure the engine IS running when everything kills out? What you describe SOUNDS like he engine is shutting down (which can also be caused by a lost/poor signal from the crank sensor - even the stumbling). I don't think the tires have anything to do with it.

All that being said, when I had a similar problem with my Ranger, I finally figured out it was the MAF that was causing the problem (was also not getting any codes). I don't remember how I figured out it was the MAF, and one major difference is that the truck never randomly shut down like yours.

I had a Saab years ago that had an intermittent crank sensor that DID randomly shut down for a few seconds and kick back in - especially at highway speeds (and was periodically hard to start because of it as well).

 

The ECT and Speedometer are big clues here.

And you say you don’t have a Check Engine light?

 

The tach and temp dropping out, airbag, and VSC light all happening at the same time would seem to me like a low voltage issue, something funky going on with the data lines, or something goofy in the cluster or PCM.
Whether or not it's related to the intermittent no start is hard to say.

When it doesn't start do you get a flashing security light with the key on?

 

There's no check engine light and there's no codes stored in the system.

 

No, mine isn't equipped with the immobilizer system.

 

Sounds like a manual inspection of the wiring harnesses is needed to check for any potential short to ground problems.

 

OP, do you have anything like an ultragauge plug into the OBD port?

 

Unfortunately no. I've got a very basic code reader that will read and reset the CEL and tell me if certain sensors are working or not. It'll also read the data stored when a code is thrown that tells you things like rpm and sensor data, but that only works if there's a code in the system. No live data for me

 

Okay, so, it's been awhile since anyone has posted to this thread, so I figured I'd update on the situation for anyone who might still be reading this...
Last month I went ahead with replacing the Crankshaft Position Sensor, which took about 4 hours due to the A/C compressor being conveniently mounted in the way of the sensor itself...don't you love Toyota engineers?
Within a couple days and the weather becoming increasingly warm, the same issue popped up yet again.
So obviously, the sensor was not the issue. More recently, I made a discovery that makes complete sense as to why I'm having starting issues. Below is a picture of the dash when the truck cranks but refuses to start. Normally, in an ignition on, engine off condition the check engine light would remain illuminated. However, as you can see, instead of a check engine light, I get a solid traction control light:



Now, I learned from another thread that the lack of a CEL in this condition means that the ECU is not communicating. This narrows down my issue to be either electrical or the result of a failing ECU. One thing I also noticed is that as soon as I plug in an OBDII code reader, the ECU magically starts to communicate again; the CEL will illuminate and the traction control light will turn off, and usually the truck will start. It won't always stay running, however, as even with the code reader plugged in, the ECU will sometimes shut down again resulting in the same pattern of lights on the dash and the tach and coolant temperature gauge bottoming out, and a stalling engine...
My best guess at this point is that the ECU is overheating since this issue only seems to happen when the temperature inside the cab is hot enough to cause heat stroke. The vehicle has only died on me at night when I had the heater running.

 

You saying it works with a scanner plugged in leads me to think there's a bad ground somewhere because scanners typically jumper chassis ground (pin 4) and sensor ground (pin 5) together at the DLC. Easy test connect one lead of your meter to the negative terminal of the battery and the other to pin 4 and then pin 5 of the DLC, it should read less than 0.2v.

 

Thank you for the info, I will definitely look into this as soon as I can. As I mentioned, the ECU doesn't necessarily stay running when the scanner is plugged in, it just gets it to "reset" as soon as I plug it in so I can start the vehicle. With that being said, could this still be the case? Also, could cab temperature have an effect on bad grounds? Not trying to nitpick, just covering my bases. I'll try the jumper test next time it gives me trouble

 

Temeperature can absolutely affect electrical connections but it can affect failing modules as well.
I would for certain verify powers and grounds at the PCM before calling it bad.

 

I forgot to mention in my post. With my Ranger, there was a brief time when everything would randomly shut down, but it would be brief. It only happened occasionally, until one day it did nothing - no crank, no dash lights, no OBD comm, etc.

After checking 5v and ground, I wasn't getting any 5v at all. Pulled the top of the main fuse box to look at the underside, and lo and behold one connector (I forget which one) completely corroded off the wire. Redid the connector - all fixed.

 

So it's been awhile since I've posted to this thread, but recently I made a new discovery with this issue. I had previously mentioned that plugging an OBD tool into the port seems to "reset" the PCM if you would.... as it turns out, the scan tool has nothing to do with it, as simply putting pressure on the OBD port with my fingers will get it working.

Once again I am asking for help. Does anyone have a wiring diagram or an idea of what ground or other wiring connections in the vicinity of the OBD port I should look into? I disassembled the dash a few weeks ago in an attempt to look for the culprit connection, but was unsuccessful. It seems once I get the PCM communicating again, it's hard to get it to stop working, and it only seems to stop working on its own, usually when the cab temperature is hot. I've jiggled wires around with no luck in finding the culprit.

 

https://www.tacomaworld.com/threads/2015-wiring.559639/