OBD-II trouble code
P0746: Pressure Control Solenoid "A" Performance or Stuck Off
Solenoid A is normally the main line pressure regulator, so its failure is felt everywhere at once rather than on one shift. Before reading the symptom, find out whether this solenoid is normally high or normally low — the two designs fail in opposite directions.
Quick facts
- System
- Powertrain
- Category
- Transmission / Pressure Control
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $150 – $1,400
- DIY difficulty
- Shop recommended
What does P0746 mean?
On the large majority of automatic transmissions, pressure control solenoid "A" is the one that sets mainline pressure — the pressure that applies every clutch and every band in the unit. It is often called the EPC or line pressure solenoid, and it is the single most consequential hydraulic actuator in the transmission. This code sets when the module commands a line pressure and the transmission does not behave as though it got it. The circuit can pass an electrical test and still store this code, because what is being judged here is hydraulic result, not continuity.
The fact that this solenoid governs the whole unit is what makes the code readable. A line pressure fault is global. Every shift is affected, in every gear, in every drive range, and usually the torque converter clutch as well. That gives you a genuinely useful sorting rule before any tool comes out: if the complaint is confined to a single shift, one gear range, or one condition, mainline pressure is probably not the problem and something more selective is. Conversely, a transmission that shifts badly everywhere all the time fits this code exactly.
The part that most often gets misread is the direction of the failure, and getting it wrong sends people to the wrong conclusion entirely. Manufacturers do not agree on the resting state of this solenoid. Many designs make it normally high, meaning a de-energised solenoid produces maximum line pressure — a deliberate fail-safe, so that a dead solenoid gives a transmission that bangs into gear violently but does not burn its clutches. Other designs make it normally low, where a failed solenoid means little or no pressure, slipping, and a unit that will destroy itself quickly. So the same words "stuck off" describe brutally harsh shifting on one transmission and slipping on another. Establish which convention this transmission uses before drawing any conclusion from how it drives, because the assumption alone can cost a rebuild.
The measurement that settles it is mechanical. Most transmissions have a line pressure test port, and a mechanical gauge fitted there gives you a real number to compare against what the module says it commanded and what the module says it is seeing. When those three disagree, the gauge is the honest one. It also separates the two big families of cause: if commanded pressure is high and actual pressure is low, something is bleeding it off — a worn valve body bore, a failed seal, a clogged filter, a tired pump — and the solenoid may be blameless. If commanded and actual track each other but neither matches what the transmission needs, the fault is upstream in the control.
Fluid comes first regardless, and not as a formality. Level, colour and smell are free to check, and low or oxidised fluid produces exactly this code by two mechanisms at once: the pump aerates and cannot build pressure, and varnish makes the regulating valve stick in its bore. A proper fluid and filter service resolves a real share of these, and it is the only step that is cheap enough to do speculatively.
Urgency here is higher than for the more selective pressure codes. If this transmission is a normally-low design and line pressure is genuinely down, every clutch in the unit is slipping under load, slip generates heat, and heat is what turns a solenoid job into a rebuild. Treat continued driving as something to minimise rather than something to manage.
Common causes
- Low fluid level, causing pump aeration and an inability to build mainline pressure
- Oxidised or burnt fluid leaving varnish that makes the pressure regulating valve stick in its bore
- Worn valve body bore around the pressure regulator, bleeding line pressure off across the whole unit
- Failed or drifting pressure control solenoid A no longer matching its commanded current to a pressure
- Restricted filter or a collapsed pickup starving the pump
- Worn pump or pump bushing unable to deliver rated flow
- Failed sealing rings or a leaking accumulator affecting the main circuit
- Wiring or connector fault in the solenoid feed that changes the current the coil actually receives
- General internal wear that lowers achievable pressure across every circuit
Symptoms
- Poor shift quality in every gear and every drive range rather than on one specific shift
- Very harsh, banging engagements on designs where the solenoid defaults to maximum pressure
- Slipping under load and rising transmission temperature on designs where it defaults to low pressure
- Torque converter clutch behaving abnormally alongside the shift complaint
- Limp mode with the transmission held in a single gear
- Transmission temperature warning or fluid that smells burnt
- Fuel economy falling noticeably as clutches or the converter slip
- Shift quality that gets worse as the fluid warms up
Diagnostic steps
- 1.Check fluid level, colour and smell before anything else. Low or oxidised fluid causes this code by two separate mechanisms and is the only cause cheap enough to address speculatively.
- 2.Establish whether this transmission's pressure control solenoid A is normally high or normally low. The same fault produces opposite symptoms on the two designs and the assumption alone can send the diagnosis the wrong way.
- 3.Ask whether the complaint is global or selective. Bad shifts everywhere fit mainline pressure; a single bad shift usually does not, and points at a different circuit.
- 4.Fit a mechanical gauge to the line pressure test port and compare actual pressure against what the module commanded across idle, drive and a light-throttle pull.
- 5.If commanded pressure is high while actual pressure is low, look for the leak path — valve body wear, seals, filter restriction or a tired pump — rather than at the solenoid.
- 6.Read commanded and actual pressure on the scan tool alongside the gauge. Where the three numbers disagree, trust the gauge.
- 7.Check the solenoid's electrical feed and connector, since a change in delivered current changes delivered pressure without any hydraulic fault existing.
- 8.Resistance-check the solenoid against specification, understanding that a solenoid can be electrically correct and hydraulically useless.
- 9.Drop the pan and inspect the filter and magnet. Clutch material on the magnet changes the conversation from a solenoid repair to an assessment of the whole unit.
Repair cost
$150 – $1,400
A fluid and filter service is $150 to $350 and is the correct first move. A line pressure test with a mechanical gauge adds $80 to $200 of labour and is worth every bit of it, because it is what separates a solenoid job from a valve body job. Solenoid replacement runs $250 to $700 depending on whether it is externally accessible or behind the pan. Valve body repair or replacement is $500 to $1,400. The reason this code is worth treating urgently rather than monitoring is what sits beyond that range: a transmission run on low mainline pressure is slipping every clutch it has, and the rebuild that follows is $2,500 to $5,500.
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
Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.