P1780
Universal (All Makes) Vehicle (OBD-II)
Severity:What Does This Error Mean?
P1780 is an overdrive cancel switch circuit malfunction code seen on Toyota and Lexus vehicles. The overdrive cancel switch lets the driver disable overdrive gear from a dash-mounted button. The PCM monitors this switch circuit. When the signal is out of range or stuck, P1780 is stored. You may notice the OD OFF light staying on, or the transmission refusing to enter overdrive.
Affected Models
- Common in Toyota Camry, Tacoma, and 4Runner
- Common in Toyota Land Cruiser and Sequoia
- Common in Lexus GX and LX series
- Seen in older Toyota Tundra models
Common Causes
- Faulty overdrive cancel switch — worn contacts or internal failure
- Damaged wiring or connector leading to the overdrive switch
- Short circuit in the overdrive switch signal wire
- Incorrect resistance reading due to moisture or corrosion in the connector
- PCM input circuit fault misreading the switch signal
How to Fix It
-
Locate the overdrive cancel switch — on most Toyota models it is on the shifter or the steering column stalk.
Refer to your owner's manual if you are unsure where the overdrive switch is on your specific model.
-
Press the switch multiple times and observe the OD OFF indicator light on the dashboard.
If the light does not respond to the switch being pressed, the switch is likely faulty.
-
Inspect the wiring connector at the switch for corrosion, bent pins, or moisture.
Moisture intrusion in the center console area is a common cause of switch circuit faults.
-
Test the switch with a multimeter for continuity in each position — open when not pressed, closed when pressed.
A switch that does not change resistance when operated is definitively failed.
-
Replace the overdrive cancel switch if it fails the continuity test or is visibly damaged.
On most Toyota vehicles this is an inexpensive, bolt-on replacement requiring no special tools.
When to Call a Professional
Overdrive cancel switch replacement is $20 to $60 in parts. Labor is minimal — usually under one hour. Wiring repair adds $50 to $150 depending on the extent of damage. This is generally a low-cost repair.
Frequently Asked Questions
Will P1780 stop my transmission from using overdrive?
It can. If the PCM detects a fault in the overdrive switch circuit, it may default to keeping overdrive disabled as a safety measure. This results in the engine running at higher RPM on the highway and worse fuel economy.
Can I just unplug the overdrive switch to fix P1780?
No — unplugging the switch will likely keep the fault code active. The PCM expects to see a valid signal from the switch. An unplugged switch creates an open circuit, which the PCM also detects as a fault.
Is P1780 an emissions-related fault?
Not directly. P1780 is a transmission/driveability code, not an emissions code. However, it will still illuminate the check engine light, which will cause an automatic failure on an emissions (smog) test.