P1820 — Transmission Transfer Case Clockwise Shift Relay Coil Circuit Failure

What Does P1820 Mean?

P1820 is a manufacturer-specific diagnostic trouble code: Transmission Transfer Case Clockwise Shift Relay Coil Circuit Failure. This code applies to FORD, LINCOLN, MERCURY, OTHER, VOLKSWAGEN vehicles. Unlike generic OBD-II codes, manufacturer-specific codes are defined by the vehicle maker and may only apply to certain makes and models.

Symptoms of P1820

⚠️ Check Engine Light (MIL) illuminated
⚠️ Erratic Transmission Transfer Case Clockwise Shift Relay Coil readings
⚠️ Related system operating intermittently
⚠️ Reduced engine performance

Common Causes

🔍 Wiring issue in Transmission Transfer Case Clockwise Shift Relay Coil circuit (damaged, chafed, or corroded)
🔍 Faulty Transmission Transfer Case Clockwise Shift Relay Coil connector or terminal
🔍 Failed Transmission Transfer Case Clockwise Shift Relay Coil
🔍 ECM/PCM connection issue

Frequently Asked Questions

What does P1820 mean?

P1820 indicates: Transmission Transfer Case Clockwise Shift Relay Coil Circuit Failure. The vehicle's computer has detected that the Transmission Transfer Case Clockwise Shift Relay Coil is not operating within its expected parameters and stored this diagnostic trouble code.

Can I drive with code P1820?

You can drive short distances for essential trips, but schedule a diagnosis soon. Driving with P1820 for extended periods may cause additional problems.

How much does it cost to fix P1820?

Repair costs for P1820 typically range from $80 to $300, depending on the root cause. Simple wiring or connector repairs are on the lower end, while component replacement costs more. A proper diagnosis ($80–$150 at most shops) will identify the exact cause before committing to expensive parts.

What To Do Next

Possible Fixes

🔧 Inspect and repair Transmission Transfer Case Clockwise Shift Relay Coil wiring and connectors
🔧 Replace faulty Transmission Transfer Case Clockwise Shift Relay Coil

1
Find your vehicle above
Click your make and model for real owner reports and common causes specific to your vehicle.
2
Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
3
Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.

P1820: Transmission Transfer Case Clockwise Shift Relay Coil Circuit Failure