Dreaded TRAC OFF and VSC TRAC and Check Engine Lights

Gentlemen,

Posting this here since I assume this is also a Tundra problem...

My new-to-me '07 Sequoia is throwing the three codes mentioned in the title. I would swear the TRAC OFF and VCS TRAC lights have NOT come on by themselves. It always happens along with the CEL. I can clear the CEL with my Torque app, but the other two lights remain on. If I clear the TRAC OFF and VSC TRAC lights by putting the truck in Neutral, shutting it off, and restarting, those lights will come back on immediately if the CEL comes on, too.

The CEL throws P0420, P0430, and P0174 codes, probably due to these https://www.tundras.com/threads/are-these-cats-going-to-be-a-problem.155324/

What is the current, prevailing wisdom on the three codes happening simultaneously? I just got the truck and am very happy with its overall condition, but I need to fix this.

Since I'm sure these faults happen simultaneously, do I actually have issues with the traction control system, or is it some kind of electrical gremlin?

Thanks much,

 

You might have better luck in the 2nd Gen Tundra forum.

 

'07 Seq is 1st gen.

'00-'06 Tundra
'00-'07 Sequoia

It fits.

 

Thanks. Didn't realize that '07 Sequoia was still 1st Gen.

 

Toyota had to finish getting rid of the inferior non-AC/RC parts.

 

I'm hopeful this isn't the end of the thread...

 

It’s normal for Toyota vehicles with VSC to illuminate the Trac and VSC lights with the CEL, at least for many engine faults.

Trac and VSC are disabled with active engine faults as they require control of the engine that may not be possible with an active fault.

I’d be going after that P0174 first, but since you recently bought from a dealer are they going good for the repairs? I suspect that the vehicle was a victim of cat theft, maybe not too long ago by how it appears from your photo in the other thread.

 

Sir,

That's exactly what I needed to know--I DO have a problem when the three lights illuminate.

I was leaning towards the same stolen cat scenario, but the Carfax did state it stopped passing emissions testing.

I doubt the (used car) dealer would pay for the repairs--I believe they let me steal the truck because they knew, but I don't know for sure they knew... However, I would have bought it anyway for the price, miles, pictures, and Carfax if they'd told me about the lights beforehand. That said, the pics they had online showed the outer bolsters of the bottom of the front seats on both sides had split. The dealer repaired both seats before shipping me the truck, no charge. The truck is seriously worth saving. And I'm not unhappy.

I know I can fix whatever, IF I can identify the problem, which is why I'm here.

 

Agree with @landphil regarding P0174.
As for the 174, it being a lean code and aside from simple checks like vacuum leaks, exhaust leaks, or a dirty MAF, lean codes can't really be diagnosed properly without a scan tool to read at a minimum fuel trims, O2, and MAF data as well as possibly a fuel pressure gauge.

and while it doesn't help much from 07 Sequoia OM....

"The “TRAC OFF” indicator light will come
on when the “VSC TRAC” warning light
comes on even if the “TRAC OFF” switch
is not pushed."

 

And that lean code on that one cylinder could be any number of things. Let's think/talk about if for a sec.

I say this a lot, but the fundamental reality with misfires is this, cause-wise, for virtually ALL of the EFI engines you'll find out there:

• You have unexpected air (leak, blockage) or bad air readings (MAF, throttle position) causing the engine create bad mixtures that doesn't fire as expected
• You have a fuel delivery issue, either injectors, fuel pump, pressure regulator, etc.
• You have a spark delivery issue, either bad coil pack, wrong spark plug, loose spark plug (or plug hole threads stripped), mis-gapped spark plug, bad spark plug
• You have a timing issue
• Highly unlikely, but it can be a computer/wiring issue, but it's super rare for that to mpact one cylinder unless the harness is whack, and these plastic coil clips on the harness DO get brittle after 15+ years!

Think about that a bit deeper:

• If it was ALL cylinders, what supplies all cylinders with air readings, air or fuel? Fuel pump would be my first guess, MAF could be tossing the ECU bad info, or the throttle assembly could be giving bad position info, or is dirty. I'd clean MAF with MAF cleaner, clean TB with a rag and TB cleaner, check fuel pressure, pull the negative battery cable for 10 minutes to force a re-learn.
• If it was only cylinders on one side of the engine, given the 2UZ has fuel pressure regulators for both sides independently (IIRC), I'd be suspicions of those, or potentially the vacuum/recovery line attached to the regulator
• If it was only a couple of adjacent cylinders on one side of the engine, I'd be suspicious of a gasket before anything else
• If it's only one cylinder ... chances are it's none of the above, possibly a gasket, but more likely injector/spark related

If you wanted a no-brainer-only-effort sanity check and you're comfortable with it, but you don't want to use extra tools or even leave the house, then (A) swap the injector on cylinder 4 (2nd cylinder, passenger side) with the injector on cylinder 2 (cylinder 1 closest to radiator, passenger side) and then (B) likewise swap the coil pack from cylinder 1 (cylinder nearest the battery) and cylinder 4. Make sure you get all the parts of the injector.

If you see the code move to cylinder 2, you know your injector that's now on #2 is dying and it's the source of your issue. If the code jumps to cylinder 1, you know your coil pack is bad. You may also consider swapping the spark plug on cylinder 6 (cylinder one step toward firewall on passenger side) with cylinder 4, and if the code jumps to cylinder 6, you know it's the spark plug. With how many counterfeits get sold by fleaBay and scAmazon these days, you never know. Replace the injector or coil pack with genuine product and move on. If the code stays, you know it's an inherent issue with cylinder 4.

If you really want to know definitively if it's due to extra air in the cylinder/intake chamber, your best place to start would be with a compression/leakdown test; make sure there's not a compression problem in that cylinder where extra air or otherwise may be getting in. This is something you can pretty easily do on your own with a borrowed kit from the parts store. Can link YouTube if needed. Really, you only need to test that one cylinder, and that brings me to the other thing I was going to mention.

You should probably check that spark plug on cylinder 4 to make sure it's not loose, and it's fully intact. If truly burning lean, the spark plug may appear creamy-coffee-tan and dry on the tip.

Let's hope this is a simple case of loose plug. But if not, make those 3 swaps to see if the code changes - noting that the last digit of the code (174, 172, 177, 176) tells you which cylinder is misfiring (4, 2, 7, or 6 in those examples).

Clear as mud?

 

@Shifty, P0174 is Bank 2 lean, not cylinder 4 lean. You getting mixed up with P03xx misfire faults maybe? They call out the cylinder number with the last digit like you describe.

I’d be testing for any vacuum leaks, checking fuel trims and the bank 2 A/F ratio sensor (aka upstream 02 sensor).

A compression test and checking plugs wouldn’t hurt, but I doubt there’s a major issue there without any missfire faults.

 

Yes, unfortunately! P0304 is what my brain interpreted. My bad.

But the info still applies, so I'm leaving it, specifically the bulleted items.

And I also agree with you. O2 sensor upstream bank 2. Possibly the vacuum line from passenger fuel regulator to square part of intake tube cracked or loose. Fuel line loose between bank 1 and bank 2 fuel rail. Fuel pressure regulator failed bank 2.

Smoke test could suss out vacuum issue.

Per FSM, whole gamut of potential problems - I was actually surprised to see the ECT (engine coolant temp sensor) in this list!:

​

 

Gents,

I believe the truck had very few miles put on it for the year or so before I acquired it. Could that be causing the P0174?

I put some 93 octane gas in her, and a large bottle of Techron. It runs well, even when the CEL is on.

Thanks,

 

List of things to check for P0174 (straight from Toyota's Factory Service Manual/FSM) is in my last reply.

That said, first thing I'd check is vacuum hoses. First hose I would check is the one that supplies vacuum to the fuel pressure regulator on the passenger bank, which is running lean. It's this hose, with a traver in orange. You want to check it's attached above all else, and also make sure the hose isn't rotten/cracked.

Yours may not look identical, but it's going to be coming from the same place and terminating approximately to the same place. Make sure the hose doesn't have cracks in it. This vacuum line (IIRC) essentially engages the fuel pressure regulator to open/close the fuel supply into bank 2 (which is throwing the lean code), and also acts as a vapor return for unburnt fuel that may escape the regulator.

​

 

shifty,

I really appreciate your inputs, and will do, or have done, the things you previously suggested. I was seriously asking if sitting undriven for many months could cause the P0174.

 

Anything chan happen if a vehicle sits long enough. Bad gas is bad news. But the fact rodents love the plastics on these vehicles so much doesn't help. And gaskets ... especially rubber ones, which is what is used between the intake manifold and head, tend to shrink/rot/crack with lack of use. Saying that "in general", not necessarily on these trucks.

 

Good question....According to what the ECT is reporting to ECU determines how much fuel to deliver and ignition timing. The temp direction an ECT is wrongly reporting gives you either System too Lean or Rich.

 

My wave runner sits idle for a few month in the winter. I some marine Stabil or Startron in the last tank of the season and then try to run it down to 1/4 tank or less before putting it away in the fall.

 

I purchased an Autel MaxiCheck MX808S bi-directional scanner. I always wanted one... What live data should I be looking for to help me solve this?

Thanks,