P2784 code meaning
Input/Turbine Speed Sensor A/B Correlation
Powertrain system Generic code P27xx codes Check engine light
What P2784 means
P2784 belongs to transmissions with two input or turbine speed sensors whose readings can be compared. When both are healthy their values agree, or differ only by a known ratio; P2784 is set when they drift apart for longer than the module tolerates while each circuit on its own looks fine. No manufacturer documents P2784 publicly, so it stays open which sensor pairs are compared in practice. The individual circuits have their own codes: P0715 family for sensor A and P2765 to P2768 for sensor B. Mitsubishi's 2019 CVT shows how sensor B can be the turbine sensor, diagnosed when it reads below 150 rpm for 5 s while the primary pulley turns faster than 500 rpm. Metal debris on a magnetic tip, a loose sensor or a damaged tone wheel are typical causes.
P2784 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 6 hours
- Clears after repairAfter a drive cycle
Symptoms of P2784
- Harsh or erratic shifts
- Emergency mode with fixed gear
- MIL on
Common causes of P2784
- Most likelyMetal debris on a magnetic speed sensor tip
- PossibleOne sensor giving a weak or distorted signal
- Less likelyDamaged tone wheel or excessive air gap
- Less likelySignal interference from poor shielding or connectors
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Input shaft speed sensor aInput shaft speed sensor bTone wheel
What each part of P2784 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 7 | Area: transmission. |
| 84 | The exact fault in that area. |
What to do next
- Note P2784 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2784
What does P2784 mean?
P2784 means "Input/Turbine Speed Sensor A/B Correlation". P2784 belongs to transmissions with two input or turbine speed sensors whose readings can be compared. It is a generic code, so it means the same on every make.
Is it safe to drive with P2784?
Drive gently and only to a workshop. With P2784 the car can go into limp mode (reduced power) to protect itself.
Will P2784 fail an emissions test?
Yes, it can. P2784 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2784 to fix?
Difficulty: hard. A typical repair takes 0.5 to 6 hours of work. This is a job for a workshop.
Will P2784 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.