As a car expert, I understand how frustrating it can be when your car starts acting up. One of the most common issues that car owners face is the P1787 P/ES Circuit Out Of Self Test Ranget error code. This error code can be caused by a variety of issues, including a faulty transmission range sensor, a damaged wiring harness, or a malfunctioning PCM. In this article, I will provide you with a step-by-step guide on how to fix the P1787 error code and get your car back on the road.
Step 1: Check the Transmission Range Sensor
The first step in fixing the P1787 error code is to check the transmission range sensor. This sensor is responsible for telling the PCM what gear the car is in. If the sensor is faulty, it can cause the PCM to think that the car is in the wrong gear, which can trigger the P1787 error code.
To check the transmission range sensor, you will need to locate it on your car. The sensor is usually located on the side of the transmission, near the shift linkage. Once you have located the sensor, use a multimeter to test it. Set the multimeter to the resistance setting and touch the probes to the sensor’s terminals. If the sensor is working correctly, it should have a resistance of around 1.5k ohms.
If the sensor is faulty, you will need to replace it. You can purchase a new sensor from your local auto parts store or online. Once you have the new sensor, remove the old one and install the new one in its place. Be sure to connect all the wires correctly and test the sensor again to ensure that it is working correctly.
Step 2: Check the Wiring Harness
If the transmission range sensor is working correctly, the next step is to check the wiring harness. The wiring harness is responsible for transmitting the sensor’s signals to the PCM. If the wiring harness is damaged or has a loose connection, it can cause the PCM to receive incorrect signals, which can trigger the P1787 error code.
To check the wiring harness, you will need to inspect it for any damage or loose connections. Start by visually inspecting the harness for any signs of damage, such as frayed wires or broken connectors. If you don’t see any damage, use a multimeter to test the continuity of the wires. Touch the probes to each wire’s end and check for continuity. If you find a wire that doesn’t have continuity, you will need to repair or replace it.
Step 3: Check the PCM
If the transmission range sensor and wiring harness are both working correctly, the final step is to check the PCM. The PCM is responsible for receiving signals from the transmission range sensor and controlling the transmission’s shifting. If the PCM is malfunctioning, it can cause the P1787 error code.
To check the PCM, you will need to use a diagnostic scanner. Connect the scanner to your car’s OBD-II port and follow the instructions to read the error codes. If the scanner shows that the PCM is malfunctioning, you will need to replace it. You can purchase a new PCM from your local auto parts store or online. Once you have the new PCM, remove the old one and install the new one in its place. Be sure to follow the manufacturer’s instructions for programming the new PCM.
Fixing the P1787 error code can be a daunting task, but with the right tools and knowledge, it can be done. By following the steps outlined in this article, you can diagnose and fix the issue, getting your car back on the road in no time.
1. Can I drive my car with the P1787 error code?
It is not recommended to drive your car with the P1787 error code. This error code can cause your car to shift incorrectly, which can lead to further damage to your transmission.
2. How much does it cost to fix the P1787 error code?
The cost of fixing the P1787 error code can vary depending on the cause of the issue. If it is a simple fix, such as a faulty sensor, it can cost as little as $50. However, if the issue is more complex, such as a malfunctioning PCM, it can cost upwards of $500.
3. Can I fix the P1787 error code myself?
If you have experience working on cars and have the right tools, you can fix the P1787 error code yourself. However, if you are not confident in your abilities, it is recommended to take your car to a professional mechanic.