P1777 often puts the CVT in limp mode - drive only as far as needed to get it looked at, since continued driving can cause more damage. P1777 is a Mitsubishi transmission code meaning the TCM found an electrical fault - an open or short - in the CVT stepper-motor circuit. The stepper motor sits inside the valve body and positions the valve that sets the CVT's ratio; when the TCM can't drive one of its coils correctly for even a fraction of a second, it stores P1777 and the transmission usually drops into a limp / fail-safe mode.
What P1777 means
Mitsubishi's CVT (JATCO CVT8) uses a stepper motor inside the valve body to move the ratio-control valve. The TCM continuously watches the voltage on each of the stepper motor's coils; if the commanded on/off voltage isn't seen (roughly 2.8 V or less when it should be on, or more than 2.8 V when it should be off) for about 0.2 seconds, it judges an open or short circuit and sets P1777. Because the stepper motor is built into the valve body assembly, the fault is usually the valve body itself, its wiring and connectors, or the TCM.
Symptoms
- Transmission limp mode or stuck in a fixed ratio
- Harsh shifting or no ratio change
- Reduced power
- Check-engine light on
- Often stored together with P1778 and other CVT codes
Common causes
- Faulty stepper motor inside the valve body assembly
- Damaged wiring or connectors between the TCM and the CVT (connectors B-120 / C-130)
- Poor connector contact or corrosion
- An internal short in the stepper-motor circuit
- A faulty TCM
Severity & driving advice
Severity: High — Usually triggers CVT limp mode; continued driving risks further transmission damage.
Can I drive? P1777 often puts the CVT in limp mode - drive only as far as needed to get it looked at, since continued driving can cause more damage.
Diagnostic approach
- Read all transmission codes — P1777 and P1778 are often stored together; note every CVT code present.
- Inspect the connectors — Check the CVT assembly and TCM connectors for bent, corroded or loose terminals and repair any contact problem.
- Test the wiring — Check the harness between the TCM and the stepper motor for an open circuit and for a short to ground.
- Repair and recheck — Fix any wiring or connector fault found and re-test before condemning internal parts.
- Replace the valve body if internal — If the wiring is good, the stepper motor is internal to the valve body assembly, so the valve body is replaced.
- Clear and road-test — Clear the codes, road-test, and confirm the CVT shifts smoothly through its full ratio range.
Estimated repair costs
Typical US repair costs (parts & labour) for the faults behind P1777. These are national-average estimates, not a quote— your actual price varies by region, shop labour rate, and your vehicle’s make, model and year. Figures reviewed 2026.
| Repair | Estimated cost (USD) |
|---|---|
| Diagnosis (scan and inspection) | $90–$150 |
| Wiring/connector repair | $90–$300 |
| Valve body assembly (with stepper motor) | $700–$1,500 |
| TCM replacement | $500–$900 |
Make & model notes
Mitsubishi: Seen on Mitsubishi JATCO CVT8 vehicles including the Outlander Sport / ASX / RVR (GA0). The stepper motor is inside the valve body, so P1777 (circuit) and P1778 (function) usually resolve at the valve body, its wiring, or the TCM.
FAQ
Can the stepper motor be replaced on its own?
No - it's built into the valve body assembly, so the valve body is serviced as a unit.
What's the difference between P1777 and P1778?
P1777 is an electrical circuit fault (open/short) of the stepper motor; P1778 is a functional fault where the motor isn't achieving the commanded ratio.
Can I drive with P1777?
It usually forces limp mode. Drive only as far as necessary - continued driving risks further CVT damage.
Does P1777 mean the whole CVT is bad?
Usually not - it typically points to the valve body (stepper motor) or its wiring, not the entire transaxle.