P0377 - OBD Trouble Code

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P0377 is a diagnostic trouble code (DTC) for "Timing Reference High Resolution Signal B Too Few Pulses". This code is stored when is set when the PCM detects the engine position sensor "B" is producing a signal with too few pulses and the "B" indicates the problem is with a portion of the system circuit instead of a particular symptom or component. Though the severity of this code is moderate to severe so it is advisable to resolve this code as soon as possible because if you keep running your vehicle with this existing code, it may lead to serious engine damage in future.

OBD-II Code Decreased engine performance is defined as a Timing Reference High Resolution Signal "B" Too Few Pulses. It indicates that PCM has detected an abnormality in the high-resolution timing reference signal. The powertrain control module (PCM) requires a timing reference signal to determine engine speed and position. This is accomplished by means of an engine position sensor, such as a crankshaft, camshaft or fuel pump position sensor. The PCM uses this information to determine fuel injector control, ignition timing and misfire diagnostics. There are two basic types of engine positions sensors: Hall-Effect and permanent magnet. Both types of sensors are triggered by a wheel or disc mounted close to the sensor. When triggered, the sensor produces a return signal which is sent back to the PCM. The PCM sends a duplicate signal of the crankshaft position sensor to the Fuel Injection Control Module (FICM). If the signal to the FICM becomes corrupt, the PCM will set code P0377.

What causes this problem with the Timing Reference High Resolution Signal B Too Few Pulses?

• Sensor failure
• Wiring issue
• Substandard Oil
• Faulty Fuel injection control module (FICM)
• Faulty Powertrain Control Module (PCM)
• Damaged reluctor wheel

1. Powertrain Control Module - The Powertrain Control Module PCM is an on-board electronic control unit that primarily controls the charging, emission and transmission systems of the vehicle. Malfunctioned PCM will always create problems so repair or replace it as required if discovered faulty.
2. Optical Sensor - Optical sensors and detectors convert incident light into an electrical signal for measurement and analysis. It should work properly to avoid any related trouble code.
3. Camshaft Position Sensor - A camshaft sensor is an integral part of the modern automobile. It is one of the devices that help the engine run smoothly which is very important for your vehicle. So, always replace the faulty camshaft sensors as soon as you discover them faulty.
4. Crankshaft Position Sensor - The crankshaft position sensor is a vital electronic device located in the engine of a car. Its purpose is to register the rate at which the crankshaft spins. For the smooth functioning of your vehicle make sure they work properly else replace them in no time

There is a possibility of a complete lack of noticeable symptoms of this error code P0377. On the other hand, these symptoms could be serious too. These symptoms may include:

• Difficult starting
• Reduced engine performance
• Low fuel mileage
• Spark knock while acceleration
• Illuminated check engine light

Please note that the Check Engine Light is usually a symptom, but not all the time. With some vehicles, the PCM will actually wait until the problem is detected multiple times before this light is activated.

The diagnostic trouble code P0377 can be complex and exhaustive to track down and repair. The task may involve multiple repairs, as well as specialized tools and equipment. If you doubt this repair is out of your skill level, it’s best to contact a qualified mechanic and have them fix this issue. The possible solutions for this trouble code include:

• Camshaft, distributor hall effect, and crankshaft sensor replacement
• Replacement of corroded or damaged wiring or connectors
• In rare circumstances, the PCM may need to be replaced

Note: There is a test drive recommended after you've completed any repairs to see if the condition is fixed. Before you take a test drive after a repair, always erase the P Code(s) first. This will turn the check engine light off and then you will know if the check engine light returns, you've got further diagnostics to complete.

Troubleshooting steps may differ depending upon manufacturer. A good starting point is always a technical service. Several tools may be required to successfully diagnose this code.

• Inspect the stored trouble code and record the freeze frame data using a scan tool.
• Clear any stored codes and take a test drive and check if the code return.
• With the help of tachometer observe the engine running to see if there is an RPM signal.
• Inspect the crankshaft position sensor, crankshaft gear, and connectors and wiring for damage.
• Test the Crankshaft Position Sensor (CPS) system to ensure the reference voltage matches specifications.
• Check for system continuity with the help of Ohmmeter.
• Check the distributor for damage, wobble, or too much end-play.

Common Mistakes When Diagnosing the P0377 Code

A full diagnosis needs to be carried out before important components like camshaft; crankshaft and distributor sensors are replaced. If a sensor needs to be replaced, it’s usually a good idea to change out both of them to avoid future problems. Unnecessary replacements of such important parts without a thorough diagnosis are fairly common.