C1239 — ABS Hydraulic Pressure Differential Switch Input Open Circuit

Q: "Can I drive with this code?"

"It depends on the severity. If the vehicle runs normally, short trips are usually OK. If you notice performance issues, drivability problems, or warning lights beyond the check engine light, get it checked soon."

Q: "Will this code clear itself?"

"Some codes clear automatically after the underlying issue is fixed and several drive cycles pass. But the root cause must be addressed first."

Q: "How do I find the exact cause?"

"A code alone doesn't pinpoint the failed part. You need a diagnostic scan ($50-150 at most shops) that reads freeze frame data and live sensor readings to identify the specific component."

What Does C1239 Mean?

C1239 is a diagnostic trouble code indicating: ABS Hydraulic Pressure Differential Switch Input Open Circuit. This code relates to the chassis system. It has been reported in NHTSA complaints across 1 different vehicle models.

Real Owner Reports

From NHTSA complaint database — actual owner descriptions.

"For the past 2 years I've had issues with the ABS, Traction, and Brake lights coming off and on on my dashboard of my 2011 Toyota Prius. Mechanics have replaced various things but have never been able to find the exact problem because the car doesn't either give any codes or it gives codes that don'"
— Toyota Prius owner, 08/01/2024

Source: NHTSA Complaints Database

Most Reported Vehicles for C1239

Based on NHTSA owner complaint data.

#	Vehicle	Reports
1	TOYOTA PRIUS

Frequently Asked Questions

Can I drive with this code?

It depends on the severity. If the vehicle runs normally, short trips are usually OK. If you notice performance issues, drivability problems, or warning lights beyond the check engine light, get it checked soon.

Will this code clear itself?

Some codes clear automatically after the underlying issue is fixed and several drive cycles pass. But the root cause must be addressed first.

How do I find the exact cause?

A code alone doesn't pinpoint the failed part. You need a diagnostic scan ($50-150 at most shops) that reads freeze frame data and live sensor readings to identify the specific component.

What To Do Next

Possible Fixes

🔧 Have the code scanned with a professional-grade scanner to read freeze frame data
🔧 If DIY repair isn't feasible, get a diagnostic from a trusted mechanic ($50-150)

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.

C1239: ABS Hydraulic Pressure Differential Switch Input Open Circuit