Sanity Check - Replace V8 Exhaust Manifold or Something Else?
 

Hey all - long time reader of the forum but first time post for help :)

I have a 2006 SR5 4WD V8 with 185k miles. Car was SoCal and CO owned, so the undercarriage is in great shape, and I've been meticulous about maintenance, etc since my ownership from 150k three years ago.

In the past year I've noticed a ticking noise, which I'm nearly 100% certain is the passenger exhaust manifold crack, get louder and louder over time. At first it didn't bother me as I would turn up the stereo and move on with my day. However, I am now having DTCs come up, as well as the VSC OFF, Traction Control, ABS, VSC TRAC, and CEL lights all show up simultaneously, which annoys me to no end.

Fix try #1 - I've bought a bluetooth OBDII scanner and cleared the codes when they come up (first couple months of DTCs). The codes/lights would go away for a few hundred miles but eventually come back up. Original codes were P0420, P0430, and P0504.

Fix try #2 - Add Dorman spark plug fouler spacer to bank 2 rear O2 sensor as this is what most 4th gen V8 owners on this forum suggested to try to "trick" the secondary O2 sensor from pulling the codes. DTCs P0156 heated oxygen sensor 2, bank 2 - circuit malfunction and P0420 came back shortly thereafter.

Fix try #3 - replace bank 2 O2 sensor with new DENSO O2 sensor ($50) along with Dorman spark plug fouler spacer. P0420 code returned

What next? I haven't replaced the rear bank 1 O2 sensor but added the spacer, like I did on bank 2, but wondering if that will even fix the DTCs or if it's something else. More than likely, I'm just ignoring the true culprit - cracked exhaust manifold - because I don't want to spend $2,000, but hoping you can help me definitively find a fix.

I'm trying to drive this car as long as possible and at 185k with recent timing belt and other extensive services, feel like a goal of six or more years at 10k miles/year is possible. But, the lights are driving me CRAZY!

I've added some screenshots of the previous trouble codes as well as catalytic converter temperatures, fuel trims, wide range equivalence ratios/voltages in case that helps. If I should look at any other areas of the OBDII scanner for values that could help track down the issue, let me know.

If it is the manifold, I live in an area where no emissions are required for registration and would be open to doing long tube headers and keeping secondary cats as to keep the repair costs as low as possible. However, If I should just run LT headers and remove secondary cats (if possible), I'm open to that too, so long as it doesn't bring the codes back.

Beyond the exhaust tick and codes/lights, truck runs perfect. A little sanity check, please?

An exhaust leak towards the front of the car can make for the cat codes as can a cat that is on the way out. I don't see how you'll get away from the p0420/430 without replacing the leaky manifolds unless you completely block the downstream o2's. These seem to often leak at the y-pipe center connection too. P0504 seems to be a brake switch malfunction.

The P0504 code has not come back since clearing the DTCs and the repair for that seems straightforward - if/when it comes back.

I included screenshots of the temperatures of the cats as I thought if a cat was failing it would run at a different temperature. Both values for primary and secondary cats are pretty well in line with one another. I'll check a leak at the Y Pipe connector, but seems pretty solid to me.

Underdog Racing used to make an O2 simulator that I would LOVE to have to code out rear O2 but not any longer. Any ideas if another company or individual makes these or has a spare laying around for purchase?

DT Headers & Y Pipe
 

Get the DT LT Headers and corresponding Y-pipe. If you live in an area that doesn't do emissions checks, get a hold of Marc @ YotaWerx Tuning and have him put a tune together for you.

I did this after eliminating all (4) cats and she runs like a scalded dog.

Unless you can find them used, DT won't have any right now. They've moved to AZ, and won't be back online for awhile.

I have my old manifolds that aren't cracked. All the way in Florida though, so I'm not much help. It would be a gamble also. They could crack like your old ones in a few thousand miles.

Six-ish month update - replaced the brake switch and haven't had any problems since. I'd have to say if someone is having similar symptoms, try the $30 part first. OBDII scanner along with the new O2 sensor and Doorman spacers and we've had zero issues (knock on wood) since replacing the brake switch.

I'm down in FL as well (Ocala) and only going to evaluate DT headers if the problem becomes obnoxious. It ticks, but if I hit the gas hard enough the roar of the V8 drowns it out!

You happen to have the part # handy for the brake switch? I recently started getting the VSC Off, Traction Control, ABS, and VSC Trac lights every so often and it's getting annoying. If I just turn the car off and restart it they always go away, but then will come back days or weeks later. Hoping it's just the switch...

From my RO, it's:

84340-69025 Genuine Toyota Switch Assy, Stop Lamp

Hope this helps!