P1391 — Glow Plug Circuit Low Input (Bank #1)

What Does P1391 Mean?

P1391 is a diagnostic trouble code indicating: Glow Plug Circuit Low Input (Bank #1). This code relates to the manufacturer-specific powertrain system. It has been reported in NHTSA complaints across 1 different vehicle models.

Symptoms of P1391

⚠️ ABS warning light on

Common Causes

🔍 Turbocharger or boost system issue

P1391 Reports by Year

2020

1

2022

1

Real Owner Reports

From NHTSA complaint database — actual owner descriptions.

"I BROUGHT MY TOYOTA PRIUS TO TOYOTA DEALER AS ABS ALERT WAS ON AND I LOST CONTROLLING THE BRAKE. TOYOTA DEALER GAVE ME AN ESTIMATE FOR REPAIR AT $2,850.00 ( P1391 ABNORMAL LEAK IN ACCUMULATOR PUMP REC MASTER CYLINDER WITH BRAKE BOOSTER AND BRAKE BOOSTER PIMP ASSEMBLY) DUE WARRANTY ENHANCEMENT EXPI"
— Toyota Prius owner, 06/01/2020

"During a hard braking, felt brake pedal softer and less responsive braking. Now ABS Icon, Brake Icon, and Traction Icon is on. Confirmed Code P1391 in ABS system."
— Toyota Prius owner, 10/21/2022

Source: NHTSA Complaints Database

Most Reported Vehicles for P1391

Based on NHTSA owner complaint data.

#	Vehicle	Reports
1	TOYOTA PRIUS

P1391 Reports by Vehicle

Detailed NHTSA complaint analysis for each vehicle model.

TOYOTA PRIUS

2 NHTSA reports · Peak: 2010, 2012

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.

P1391: Glow Plug Circuit Low Input (Bank #1)