OBD-II trouble code
P0764: Shift Solenoid "C" Intermittent
Solenoid C is dropping out and recovering. Before condemning it, count the codes: solenoids in a pack share a supply and a return, so faults on more than one channel are one shared conductor, not several failing solenoids.
Quick facts
- System
- Powertrain
- Category
- Transmission / Shift Control
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $120 – $850
- DIY difficulty
- Advanced DIY
What does P0764 mean?
P0764 is stored when the module briefly loses and regains a valid electrical picture of shift solenoid C. The most valuable thing to establish about this code is not what solenoid C does but how many other solenoid codes are sitting beside it, because that number decides the whole shape of the repair.
Shift solenoids are not wired as fully independent devices. In a solenoid pack they are grouped, and grouped devices share conductors — commonly a single supply feed to the whole assembly, with the module switching each solenoid's ground individually, or the mirror of that arrangement. Whichever way round it is done, some part of every solenoid's circuit is a conductor it does not own. That shared section is a common-cause failure point, and it produces a pattern anybody can read without a wiring diagram in front of them.
The arithmetic is simple. One solenoid code, appearing consistently, points at that channel — its winding, its individual conductor, its pin in the connector. Two or more solenoid codes appearing together, or drifting from one channel to another over successive drives, does not mean several solenoids are failing at once. Failure is not that coordinated. It means the fault is in something they have in common: the shared supply or ground, the case pass-through as a whole, or the module's own power and ground. Reading the pattern this way is the difference between a wiring repair and an unnecessary solenoid pack, and the pattern costs nothing to read.
That matters more on this code than on the earlier letters for a second reason worth understanding. The letters A and B are assigned with a good deal of consistency across manufacturers, because almost every automatic has a first and a second shift solenoid and they are numbered in the obvious order. By the time the alphabet reaches C, the assignment is far more design-specific. On one transmission solenoid C may schedule a particular shift; on another it may serve a function that has nothing to do with shift scheduling at all. Ordering "a shift solenoid C" from a parts counter without first identifying what your transmission physically calls by that name is a well-established way to fit the wrong component, and it is the reason service data should be consulted before a part number is.
So the sequence here runs in a specific order. Count the codes and decide whether you are chasing one channel or a shared conductor. Then, only if it really is one channel, identify which physical solenoid your transmission designates as C. Testing before doing both of those is how people end up measuring a healthy component and drawing the wrong conclusion from an entirely correct reading.
Common causes
- Fault in the supply or ground shared by every solenoid in the pack, reported on one channel
- Degraded pin or terminal in the shared feed at the case pass-through connector
- Marginal power or ground to the module driving the solenoids
- Individual conductor to solenoid C chafed or intermittently open
- Solenoid C winding failing internally, which the code pattern will show as a single-channel fault
- Wrong solenoid previously fitted after a parts-counter lookup that did not match the transmission
- Corrosion in the connector body affecting adjacent pins at the same time
Symptoms
- Several different solenoid codes stored together rather than one repeating consistently
- The channel reporting a fault changing from one drive to the next
- Erratic shift quality with no repeatable pattern
- Intermittent limp mode that clears on restart
- Codes returning after a solenoid was replaced on a single channel
- Check engine light cycling on and off across drive cycles
- Transmission behaving normally for long periods between events
- Other transmission electrical codes appearing alongside these
Diagnostic steps
- 1.Count the solenoid codes before testing anything. One channel reporting consistently is a channel fault. Two or more channels, or a fault that moves between channels across drives, is a shared conductor — and no number of solenoids will fix it.
- 2.Identify the shared architecture in a wiring diagram for your transmission. Most packs are fed a common supply with the module switching each ground, or the reverse. Knowing which arrangement you have tells you exactly which conductor is common to the affected channels.
- 3.Test the shared conductor first when the pattern points that way. Measure the supply at the pack with the solenoids commanded, and check the return path for voltage drop under load rather than for continuity, which will pass on a connection that is failing.
- 4.Verify module power and ground before suspecting anything inside the transmission. A module with a marginal ground will report faults on the outputs it cannot control cleanly, and those look exactly like solenoid problems from the scan tool.
- 5.Only now identify which physical valve your transmission calls solenoid C. Unlike A and B, the later letters are assigned per design, and confirming the part in service data prevents a correct test being performed on the wrong component.
- 6.Confirm the fix by clearing all codes and driving several cycles. Watching which codes return, and whether they return together, retests the shared-versus-single question rather than just the component you replaced.
Repair cost
$120 – $850
Diagnosis is $120 to $250, and on this code it earns its price by answering the shared-conductor question before any part is bought. A wiring or connector repair on a shared feed is $150 to $400. An individual solenoid, where the code pattern genuinely points at one channel, is $350 to $600 fitted on transmissions where the pan drops to reach the valve body. A full solenoid pack is $500 to $850. The expensive mistake this page exists to prevent is fitting a pack because three solenoid codes were stored — three codes usually means one shared conductor, and the pack was never the problem.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with transmission shift solenoid replacement preselected. Adjust labor rate and vehicle category to fit your situation.
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.