P0378 OBD-II Trouble Code: Timing Reference High Resolution Signal B Intermittent/Erratic Pulses

Our certified mechanics come to you · Get a fair and transparent estimate upfront

Red-stars EXCELLENT RATING ON

Cost of diagnosing the P0378 code

P0378 is a diagnostic trouble code (DTC) for "Timing Reference High Resolution Signal B Intermittent/Erratic Pulses". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$20.00
Toyota$20.00
BMW$20.00
SCHEDULE P0378 DIAGNOSTIC Get a fair and transparent estimate upfront

P0378 code definition

If the PCM has stored the code P0378, it means that the system has detected an abnormal pulse reading from the high resolution timing reference signal B, which indicates that there is a fault with the system’s circuitry.

What the P0378 code means

Located in the injection pump is a sensor disk that emits pulses that the PCM uses to control fuel injection timing. The PCM tests for missed pulses, and compares those to the number of pulses it should be detecting according to the manufacturer. If this value is not correct or erratic, the PCM will store the code P0378.

What causes the P0378 code?

There are many things that could cause an erratic pulse reading between the sensor disk and the PCM. Most often, these include a defective crankshaft, camshaft, or distributor position sensors.

However, other causes may include:

  • Failure of the distributor
  • Open or shorted optical sensor
  • Faulty, corroded, damaged, open, or shorted wiring or connectors
  • Failed PCM, in rare cases

What are the symptoms of the P0378 code?

The P0378 code could be preceded by no symptoms at all besides the illumination of the Check Engine light. However, it could also be preceded by engine misfiring, knocking when accelerating, and decreased fuel economy.

How does a mechanic diagnose the P0378 code?

A mechanic should first abstract code information from the PCM with an OBD-II scanner, and check for other codes that may indicate a larger or related issue.

In order to diagnose the cause of the P0378 code, many mechanics begin by inspecting the crankshaft gear and crankshaft position sensor. This is accomplished by checking for the engine RPM signal while the engine is running. If there is no signal detected, then a visual inspection of the crankshaft and related components is necessary. The technician should repair or replace any components that are faulty. This process eliminates one of the most common issues for the P0378 code, and may help narrow the options for following repairs.

Common mistakes when diagnosing the P0378 code

When diagnosing the P0378 code, a common mistake is forgetting to clear the code and do a road test after performing each potential solution. This step should be done after each repair, to help narrow down the cause faster. By replicating the moment of failure, a mechanic may be able to discover the problem much faster.

Another common mistake with the P0378 code is automatically replacing the crankshaft, camshaft, or distributor sensors, rather than checking for mechanical distributor failure or other issues. Additionally, it is important to replace crankshaft or camshaft sensors as a set, rather than individually.

How serious is the P0378 code?

Because the P0378 code relates directly to how the PCM controls fuel injection and timing, this is a very serious issue that should be addressed immediately. Failure to address this issue when it is detected could result in the failure of other engine components when they aren’t able to obtain fuel, or correct fuel pressure.

What repairs can fix the P0378 code?

In order to address a P0378 code, there are a few repairs that a mechanic may choose to perform. These include:

In the rare case that the PCM is faulty, the mechanic may replace the PCM.

Need help with a P0378 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

P0378
trouble codes
Check Engine Light

No more waiting rooms! Our mechanics will come to you to diagnose and fix the P0378 code.

SCHEDULE P0378 DIAGNOSTIC
Get a $20 credit for the follow-up repair

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.8/5

Number of Reviews

5,156

Rating Summary
4,752
196
50
27
131
4,752
196
50
27
131

Al

21 years of experience
14 reviews
Al
21 years of experience
Nissan Pathfinder - Check Engine Light is on - Atlanta, Georgia
Al, was cool and very knowledgeable. Being direct and upfront always works. Al, is a credit to the company.

Xavier

10 years of experience
20 reviews
Xavier
10 years of experience
Chevrolet Equinox - Check Engine Light is on - Frisco, Texas
Xavier was GREAT!!! He made sure that I understood everything that he did to my vehicle and answered all my questions. Very thorough and even worked thru the light rain that we had. When I have to use this service again, I hope to be able to request him!

Luis

14 years of experience
52 reviews
Luis
14 years of experience
Kia Sorento - Check Engine Light is on - Las Vegas, Nevada
Luis did an excellent job in determining that this was a warranty issue on bad parts. He has integrity and is good at what he does. I would highly recommend him for any auto repairs that come up.

Reginald

36 years of experience
32 reviews
Reginald
36 years of experience
BMW 325i - Check Engine Light is on - Los Angeles, California
Reginald was incredibly helpful in helping me to diagnose several issues in my car, as well as repair issues to help me pass a break and light test. He even went so far as to come to the brake and light testing location so that he could ensure that the car passed and be there if anything else needed to be fixed on the spot. Absolutely would recommend him to anyone who is looking for an honest and knowledgeable mechanic!


More related articles

P2605 OBD-II Trouble Code: Intake Air Heater A Circuit
P2605 code means voltage variations have triggered the Check Engine Light due to open or shorted wires or connectors, or faulty heater element.
P0204 OBD-II Trouble Code: Injector Circuit Malfunction - Cylinder 4
P0204 code definition Injector Circuit Malfunction - Cylinder 4 What the P0204 code means The Engine Control Module (ECM) runs checks...
P2723 OBD-II Trouble Code: Clutch Pressure Control Solenoid 5 - Stuck Off
P2723 means a solenoid has malfunctioned due to low fluid levels, a failing transmission, faulty sensor or solenoid, or electrical issues or problems.

Related questions

My horn won't work

The horn being inoperative could be from either the steering wheel clock spring, or the horn assembly. Both have been known to cause the problem you described. The Check Engine Light could be on for a sensor problem, or a...

My car won't start - Hyundai Elantra

The first step that should be done is to have a certified technician, such as one from YourMechanic, download any error codes for you and diagnose your illuminated Check Engine Light. If you have a professional digital scanner, you can...

I have a 2010 Buick Enclave cxl and the engine light when on a week ago on Monday I took it to auto zone and they gave me a code f

Most emission codes will not result in a no crank condition. Once the cause of the no crank/no start fault is repaired though, you should still request a check engine light diagnostic so that the responding certified mechanic can find...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com