2008 Sienna: Constant, intermittent P0352 + thousands of $$$

[johntempleton]

2008 sienna XLE with 135k on it. 3.5L DOHC V6 w/VVT-i 5 Speed

January 2023: driving hit a pothole. Check engine comes on and I take it to dealer (was due for oil soon). Code = p0352. Replaced ignition coil.

June 2023: hit rough road (they were tearing up road for repair). Check engine comes on. Pull into Autozone for a read. P0352. Autozone clears the code or the code self-disappeared, take it to dealer. Cannot replicate the error and they played swap-the-coil.

September 2023: P0352 is back (I bought a code reader at this point). Back to dealer. Played swap-the-coil and all coils test OK. All new sparkplugs.

November 2023: P0352 is back, but this time brought even more horrors. Car is outright dying. This was the official write up.

FOUND DTC PO300 RANDOM CYLINDER MISFIRE AND P0171 SYSTEM TOO LEAN ~|~FOUND MISFIRES ON CYLINDERS 1 AND 2, MOVED COIL AND SPARK PLUGS OF CYLINDER 2 WITH NO CHANGE PERFORMED FUEL SYSTEM PRESSURE TEST, FOUND FUEL PRESSURE TO ONLY BE AT 26PSI, SPEC IS 44-49PSI. RECOMMEND REPLACEMENT OF FUEL PUMP.
Replaced fuel pump.

January 2024: Riding on a rough road. CEL. P0352 is back.

So at this point, we've got thousands of dollars in the form of:

 

 

• New coil (that is likely not even on that cylinder anymore since they switched them around).
• New spark plugs (all)
• New fuel pump

and P0352 is back.

I should note that it is driving fine, but when I code-clear P0352 comes back within 20 minutes/miles. I am not feeling or hearing ANY issues whatsoever (vs when the lean code came up and it jumped/sputtered and then just died).

Any ideas? Edited January 29 by johntempleton

[Toyota Owners Club]

Sounds like loose connections in the engine bay if the running fault is associated with bumpy roads.
Start with checking the battery connections and terminals are tight.
Check the earth leads going to the engine/trans are tight and not damaged

When the code appears again then leave running and fiddle with leads in the engine bay to see if anything changes in the way of running (Ford call this the 'wiggle test' and is by far the best way to diagnose where a fault is)