P0174 on a Toyota Highlander
P0174 means system Too Lean (Bank 2). On the Highlander, a few causes come up far more than others.
What P0174 usually means on a Highlander
P0174 is the bank 2 lean code and appears only on V6 Highlanders. It means the rear (firewall-side) cylinder bank is running lean. On its own it usually points to something specific to that bank — a cracked rear PCV hose or a leaking rear intake gasket. When it comes with P0171, the cause is generally shared between banks, such as a dirty MAF or low fuel pressure.
Most common causes on the Highlander
- Bank 2 vacuum leak
A split rear PCV hose or a leaking rear intake gasket leans just the firewall-side bank.
- Dirty MAF (with P0171)
Two lean banks at once usually trace back to one contaminated MAF.
- Failing bank 2 AF sensor
That bank's rear Denso sensor is usually original and gets lazy with age.
- Low fuel pressure
A weak pump pulls both banks lean under load; check pressure when trims climb on every bank.
What P0174 costs to fix on a Highlander
A standalone P0174 means chasing a rear-bank vacuum leak, which is fiddly because the hoses tuck behind the intake on the transverse V6, so budget for diagnostic time. A cause it shares with P0171 is easier to pin down. A smoke test is the quickest route to the leak.
Year, engine and mileage change the answer. Start a case and Redline weighs these causes against what your car shows, then names the check that would settle it.
Other codes on the Toyota Highlander
Related symptoms
Toyota Highlander problems & recalls by year
Based on widely reported patterns for this model; individual causes vary by year, engine and history. Generic P0174 behavior is covered on the main P0174 page. Confirm with a scan tool before buying parts.
P0174 on your Highlander?
Every problem becomes a Case. Tell Redline what your Highlander is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.