OBD-II trouble code
P0664: Intake Manifold Tuning Valve Control Circuit Low (Bank 2)
A short to ground on the Bank 2 tuning valve circuit. The reason this one is worth reading carefully is what it does to fuel trims: with one bank tuned and the other stuck, the two halves of the engine stop breathing alike and the resulting trim code looks exactly like a vacuum leak.
Quick facts
- System
- Powertrain
- Category
- Air Intake / Manifold Control
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $120 – $1,400
- DIY difficulty
- Advanced DIY
Browse every code in P0600–P06DD, or start from the full code library.
What does P0664 mean?
P0664 reports that the Bank 2 tuning valve control circuit is being pulled toward ground when the module expects it to be floating. The mechanisms are the familiar three — a chafed control wire, a solenoid with shorted windings, or a module driver that has failed on — and in two of those three the valve ends up energised permanently, locking that bank's intake tract into one configuration.
What deserves the attention on this code is the consequence, because it is a two-bank engine and the two banks are now behaving differently. Intake tuning changes how much air actually reaches the cylinders at a given engine speed. With Bank 1 switching normally and Bank 2 stuck, the cylinder filling on the two sides diverges, the oxygen sensors downstream report different mixtures, and the module's fuel trims for the two banks pull apart. That is a genuinely useful diagnostic signature and it is also a trap: a bank-specific lean or rich code is one of the most common reasons a vehicle gets smoke-tested for vacuum leaks, and on this fault there is no leak to find. The manifold is intact. It is simply tuned differently on one side than the other. If a bank trim code is stored alongside P0664, they are one fault, and fixing the valve resolves both.
The cause profile differs between the two banks in a way that is worth using, but it follows the geography rather than the bank number, so establish which side Bank 2 is before applying any of it. On a transverse V engine the harness on the bulkhead-side bank lives in the hottest and least ventilated part of the engine bay, is routinely draped across or near the transmission bellhousing, and sits above an exhaust manifold with little airflow over it. Insulation there hardens with heat cycling and then cracks, and the wire finds a bracket or the bellhousing to rest against. On that bank the dominant cause of a short to ground is thermal degradation and chafe. The bank facing the radiator fails differently — connector corrosion, because it is the side that gets rained on through the grille. Which of those descriptions applies to Bank 2 on this engine depends on where cylinder one sits, and on the common transverse V6 families it is frequently the accessible front head. Looking for the failure the location produces is faster than working the circuit end to end; looking for the failure the bank *number* suggests is how the wrong side gets dismantled.
One more thing worth saying to anyone about to pay for access to the buried bank. The two solenoids are the same age and have heat-cycled together for the same number of miles, and the one on the hotter, less ventilated side has had the harsher time of it. If the plenum or ducting is already off to reach the Bank 2 valve, it is worth at least measuring the Bank 1 solenoid while everything is apart. Coming back six months later to do the same dismantling for its twin is the avoidable version of this repair.
Driving on it is acceptable. Nothing is being damaged, the engine has simply lost the tuning benefit on one bank, and the trim divergence is the module compensating correctly rather than a sign of harm.
Common causes
- Bank 2 control wire chafed to ground where it crosses the bellhousing or an engine bracket
- Heat-hardened insulation cracking above the exhaust manifold on whichever bank is the hotter, less ventilated one
- Bank 2 tuning valve solenoid with internally shorted windings
- Failed module driver holding the Bank 2 circuit low
- Harness pinched or trapped during previous work on this bank, such as spark plugs or a manifold gasket
- Coolant or water intrusion into the Bank 2 solenoid connector bridging the control pin to ground
- Corrosion at a terminal where cowl drainage runs onto a firewall-side connector
- Loom rubbing on a transmission mount or dipstick tube behind the engine
- Repair splice from earlier work routed against a sharp edge
Symptoms
- Fuel trims diverging between banks rather than moving together
- A bank-specific lean or rich code stored alongside this one, often mistaken for a vacuum leak
- Check engine light on
- A flat spot at one end of the rev range, muted because only one bank is affected
- Slight unevenness under load as the two banks fill differently
- Reduced fuel economy
- The Bank 2 valve held in its energised position with the ignition on
- The code returning shortly after a new solenoid is fitted, indicating a damaged module driver
Diagnostic steps
- 1.Compare live fuel trims for both banks before doing anything mechanical. Trims that have pulled apart confirm the two banks are breathing differently and tie any bank-specific mixture code to this fault.
- 2.Resist smoke-testing for a vacuum leak on the strength of a bank trim code alone when P0664 is also stored. The trim divergence is a consequence of the stuck valve, and there is usually no leak to find.
- 3.Confirm which physical side of the engine is Bank 2 on this vehicle before removing anything, since it is defined by cylinder numbering rather than by position.
- 4.Disconnect the Bank 2 solenoid, then measure resistance from the control pin to ground rather than voltage. A voltage reading here proves little: the solenoid coil is what ties that pin to the supply, so with the valve unplugged the pin is unbiased and reads near zero on a healthy circuit as well as a shorted one. A low resistance to ground with the valve disconnected is the reading that puts the fault in the harness or the module and exonerates the valve.
- 5.Measure the Bank 2 solenoid coil resistance and compare it directly against the Bank 1 solenoid. On a two-bank engine the good side is the best reference you will get.
- 6.Inspect the harness where it crosses the bellhousing, brackets and any point close to the exhaust manifold, with the engine cold — this is the hottest part of the bay and the loom you are reaching for is the one lying against the manifold. On the buried bank, heat-cracked insulation is the leading cause and is usually visible once the loom is exposed.
- 7.Check the connector for coolant or water intrusion, particularly where cowl drainage passes over a firewall-side solenoid.
- 8.Check whether the circuit still reads low with both the solenoid and the module connector disconnected. If it does, the wiring is the fault; if it only reads low with the module connected, suspect the driver stage.
- 9.While the plenum or ducting is off, test the other bank's solenoid too. The two are the same age and the access will not be this easy again.
Repair cost
$120 – $1,400
Diagnosis is $100 to $200, at the upper end on whichever bank is the buried one because confirming a circuit you cannot see takes longer — and that is not reliably Bank 2. Repairing a chafed or heat-damaged control wire is $180 to $700, the upper end applying where the damage is behind the engine and the loom has to be opened with limited access. Replacing the Bank 2 solenoid runs $150 to $400 where it can be reached directly and $450 to $1,000 where ducting, cowl or plenum removal is required first. Connector or terminal repair is $110 to $350. If the module driver was damaged by the short, replacement and programming is $700 to $1,400. Worth factoring in: if the engine is already apart for access, adding the other bank's solenoid costs only its part price at that moment, against several hundred dollars of repeated labour if it fails later.
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DIY vs shop
This is an advanced DIY job. It typically requires specialty tools, scan-tool access, lifting equipment, or careful sequencing to avoid causing new failures. Plan for extended downtime and have a backup vehicle. Most owners are better served by a shop that has done this repair before.