How to read a code from a truck that won’t record them?

I could use some insights here.

My truck is having some kind of misfire/fuel line issue. Randomly, usually after an hour of driving, my check engine light will flicker like a horror movie light bulb in time with a small loss in engine power. Lots of stuttering. Eventually the light will stay on while driving, but be off the next time I start the vehicle. I take it in and they can’t find anything wrong with it. Last weekend after an hour of driving out of town the light came on and the car stuttered hard. Almost zero engine power- enough to maintain speed for the most part to get it a few hundred yards down the road to where I needed to go, but once parked it would only stall from a low idle if I tried to ease it into gear to move it. Had it towed. Suddenly works great for the mechanics, they can’t find anything wrong with it, no codes.

Any ideas on how to read a code that won’t log?

 

Yes. Get an OBDII reader, either by purchasing one or from a friend. Plug it in and keep it in while driving. If this situation happens again, you should then see the code pop up on the OBDII reader, even though some of the early 1st generations didn't record or log the error codes.

 

As someone stated, it might be best to buy an under 20 buck Bluetooth OBD2 reader and leave it plugged into the OBD2 port under the dash and drive, that way you have the data logged when your issue happens. Blinking MIL usually indicates that if continued to be used, the engine may sustain damage. The blinking MIL usually happens with misfires type of issues.

 

Might be unrelated, BUT. My wife has a ‘03 RAV4 that was doing very similar to what you explained. It would sputter/skip very unpredictably. The CEL would come on but when I turned the car off and cranked it back, the light would be off. It would not store any codes. I have a neighbor that is a mechanic, he has the fancy Snap-On OBD computer. We hooked it up and took a drive, when the car would sputter/skip, the computer would lose connection. So, we couldn’t get a code to show. He said the engine was basically stalling out for just a bit, not allowing the computer to read a code. We pulled out the coil packs and noticed one had a small crack along the casting line. You could barely see it. I replaced all the coil packs and spark plugs and solved the problem. Hope this helps.

 

Yes these are the common types of issues associated with the blinking MIL. Thanks for typing that up and sharing.

 

Don’t rely on a computer to tell you what is wrong... the people that have looked at you rig are NOT mechanics. A mechanic would have fixed or at least diagnosed it. Problem with the industry, if I can’t plug in I can’t fix bullshit.

As said above, take the coil packs out and examine them for cracks, check the HT leads for cracking, chews, bad contact, check the vacuum and pulse lines for any sign of collapse (had the pcv line on the 99 runner doing this...stumble,stall...no codes), check battery cables and mount points, do a battery/charging system test. Replace the spark plugs.

All this should take about 1.5 hrs to do if you take your time. Most is visual with a bit of hand work.

Oh, find a mechanic, we are still out there, usually not working for dealers or shops that rely on computers to fix shit... most of us have left due to shitty pay...

 

I agree, back to the basics,,, fire, air, fuel

 

Yes a good Bluetooth OBDII reader with an app on your phone (I personally love Torque) to record data should tell you what you need to know to get started.

Good advice. The CEL is a good STARING point, but should not be what you base your entire diagnosis on. Sometimes other problems can cause unrelated sensors to throw codes.

 

did you notice if the CEL stayed on when it died? maybe dont turn the ignition off all the way just turn the ignition to accessory then try to read the code.

 

Transmission valve body or gear selector can be cause of a misfire... usually codes as transmission failure...hence computers being only a tool. Was watching a show and they had a car code as transmission shift actuator failed or not working, they were working on the fuel system, caused the transmission to think the actuator was sticking...car was misfiring bad.

I think OP has a simple issue, HT lead or coil is bad most likely

 

Yep and if OP sticks a scanner it'll probably read a cylinder misfire which when you look up can be any number of issues from spark plugs to cracked heads. The code just tells you which sensor has triggered, and nothing else.

 

If it's throwing codes at all, it would keep those codes unless the battery is disconnected or the codes are cleared. So if you're not showing codes, then it's likely not throwing any, or your ECU is FUBAR'd

An intermittent problem like this kinda seems like a grounding issue.

 

Not all codes get stored in the ECU. If there is an intermittent issue, say loosing spark on #4 at high rpm, but returns to normal once the RPM drops (power commanders in bikes)
And the engine cycles normally for a minute or so the ECU will say the problem is non existent.

To ASSume an ECU is an FDR is foolish.

Which is why it is so hard to find a mechanic these days.

 

If it even will tell him. Live action is about the only way to hope and find something without getting dirty.

Computers are great.... and they suck ass also.

 

rather than me explain it here is an article... dated, but accurate.

https://www.motor.com/magazine-summary/advanced-mode-06-diagnostics-march-2007/

In my experience this is why I pay $$$$ for a professional code reader, yes the $100 ones work fine for basic stuff but sometimes you need to get deep into the PCM, Mode 6 is the key. Interpreting the data is another, sometimes it is sanatized and is human readable, sometimes it is hexidecmal.

yours might be the case where an experienced pro with the correct tool and knows HOW to use and read the tool can help.

addendum... I rereading and rethinking I am thinking that your PCM may be loosing its power or ground. There is one way I can see you checking this and this requires a code reader. When the PCM is cleared a code is set in the PCM, a P1000. This resets ALL of the smog monitors back to nil and the drive cycle has to be completed. If your PCM IS loosing power/ground you could be in a perpetual state of the PCM reseting itself so, no codes stored. This is a grasping straws thought... the other is that the PCM is flaky and while rare, it does occur.

good luck and keep us posted.

 

Left work at lunch today and grabbed my truck from the mechanic to try to get it to trip a code. Ran errands, got lunch, went home and took a shower (left it running), then went to autozone to get one of those USB scanners per you guys recommendation and the engine light came on in the parking lot. They scanned it for free instead while it was there and gave me three codes:

MAF
Air temperature something
Camshaft position sensor

Brought it back to mechanic and left it running till he got off lunch. He hooked up his better scanner and got about the same three codes, though his picked up something wrong with the valve timing sensor instead of the camshaft (he said something about the camshaft code being kind of a red herring without a better diagnostic).

Anyway he is going to tinker with those two items and we will go from there.

 

sweet. It is important that the actual codes be written down for reference as they are symptoms of a problem and not a "replace this part". He is correct in his analysis of the camshaft code... your truck will run with a flaky camshaft position sensor, it will also start with a flaky camshaft position sensor, it will just crank longer, like 3 seconds before it fires. Unfortunatly, unless the part(s) totaly fail the electrical tests you just might have to "replace with known good unit". Factory service manuals like to add that as the last "test" of a part.

... none of the above answers the question of why the PCM isnt storing the codes, either there is still a problem or the OBDII reader is incapable of reading "stored" codes. I hope it is the latter.

 

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That is a mystery to me. I’d love to know exactly how that all works. My best guess is they put some play in those codes specific to have to be completely fubar instead of intermittent in order to record- or maybe whatever records them is shot. Either way, unless one falls in my lap or my truck turns into Toyota Christine because of it, I’m not replacing the PCM.

 

there are hard codes and soft codes. hard codes are misfires and things similar, soft codes are usually evap related like a bad seal on a gas cap. Not all CEL (check engine light) codes are engine related. It depends on year make and model of vehicle. The shitty thing is that you can have a CEL for a non emmission related item, transmission for instance, and you cant get it smogged because the CEL is on. 1st gen Tacoma's have a minimum of ecu's that are accessable via the OBDII connector. I have never used the Toyota data link so I dont know what exatcly that has access to. Some of the high end vehicles that I tinker on have upwards of 60 ecu's, fortunatly those ancillary systems dont usually give issues. Does a sunroof REALLY need an ECU? Some manufacturers say yes. How about auto dim headlights or auto on windshield wipers...