P1847 - 2-3 Shift Solenoid Circuit High Voltage

Introduction:

The P1847 diagnostic trouble code (DTC) signals a problem with the 2-3 shift solenoid circuit in your vehicle's automatic transmission. This means the Powertrain Control Module (PCM) has detected an abnormally high voltage in the circuit controlling the solenoid responsible for executing the 2nd to 3rd gear shift. Addressing this issue promptly is crucial for maintaining proper transmission function and preventing potential damage.

Table: P1847 - 2-3 Shift Solenoid Circuit High Voltage

Detailed Explanations:

2-3 Shift Solenoid: The 2-3 shift solenoid is a crucial component within the automatic transmission responsible for controlling the hydraulic pressure that engages and disengages the 2nd to 3rd gear shift. It's essentially an electrically controlled valve that either allows or blocks the flow of transmission fluid to the appropriate clutch pack or band. When the PCM commands the shift, it energizes or de-energizes the solenoid, causing it to move and redirect the fluid.

PCM (Powertrain Control Module): The PCM is the central processing unit of your vehicle, overseeing and managing various engine and transmission functions. In the context of the P1847 code, the PCM monitors the electrical circuit connected to the 2-3 shift solenoid. It sends a signal to activate the solenoid and then monitors the voltage returning from the circuit. If the voltage is higher than expected when the solenoid is supposed to be OFF, the PCM will set the P1847 code.

Wiring Harness & Connectors: The wiring harness and connectors act as the communication network between the PCM and the 2-3 shift solenoid. They provide the pathway for electrical signals to travel, enabling the PCM to control the solenoid. Damage to the wiring, such as cuts, chafing, or corrosion, can disrupt the electrical flow and lead to a high voltage reading, triggering the P1847 code.

Transmission Fluid: Transmission fluid plays a vital role in the proper functioning of the transmission, including the operation of the shift solenoids. It lubricates moving parts, cools the transmission, and transmits hydraulic pressure. Low fluid levels or contaminated fluid can negatively impact the solenoid's performance, indirectly contributing to the P1847 code.

Hydraulic System: The transmission's hydraulic system is responsible for utilizing fluid pressure to engage and disengage the various gears. This system relies on precise fluid pressure regulation, which is controlled by the valve body and shift solenoids. Blockages, leaks, or malfunctions within the hydraulic system can affect the solenoid's ability to function correctly, potentially leading to the P1847 code.

Voltage Readings: Measuring the voltage in the 2-3 shift solenoid circuit is a crucial diagnostic step. When the solenoid is commanded OFF, you should expect to see near battery voltage (around 12-14V). When the PCM commands the solenoid ON, it typically grounds the circuit, and the voltage should drop to near 0V. A high voltage reading when the solenoid should be grounded indicates a problem with the circuit, such as a short to power or an open after the solenoid.

Testing Procedures: Diagnosing the P1847 code involves a systematic approach to identify the root cause. This typically includes a visual inspection of the wiring and connectors for damage, measuring the resistance of the solenoid to check for internal faults, checking the voltage at the solenoid connector under different conditions, and using a scan tool to activate the solenoid and monitor its response.

Scan Tool Data: A scan tool provides valuable information for diagnosing transmission issues. It can display the commanded state of the solenoid (ON or OFF), the actual voltage reading in the circuit, and other relevant data, such as transmission temperature and vehicle speed. This data helps technicians pinpoint the source of the problem and verify the effectiveness of repairs.

Related Codes: The presence of other DTCs alongside P1847 can provide valuable clues about the underlying issue. For example, codes related to other shift solenoids, transmission range sensors, or transmission temperature sensors may indicate a more widespread problem within the transmission system. Addressing all related codes is crucial for a complete repair.

Common Symptoms: While the P1847 code itself is a technical indicator, it's often accompanied by noticeable symptoms. These symptoms can include harsh or delayed 2-3 shifts, failure to shift into 3rd gear, transmission slipping, transmission overheating, and the illumination of the check engine light. These symptoms can help you identify a potential transmission problem and prompt you to seek professional diagnosis and repair.

Frequently Asked Questions:

• What does the P1847 code mean? It indicates a high voltage condition in the 2-3 shift solenoid circuit, detected by the PCM.

• Can I drive with a P1847 code? It's not recommended, as it can lead to further transmission damage. Limit driving and get it checked soon.

• How do I fix a P1847 code? Diagnosis involves checking wiring, solenoids, and the PCM. Repair often requires replacing faulty components or repairing wiring.

• Is the P1847 code a serious problem? Yes, it can lead to transmission damage if not addressed promptly.

• What are the common causes of P1847? Damaged wiring, faulty solenoid, or PCM issues are the most common causes.

Conclusion:

The P1847 code signifies a potentially serious issue within your vehicle's automatic transmission. Proper diagnosis and repair are crucial to prevent further damage and ensure smooth shifting. Consider seeking professional assistance from a qualified mechanic to address this issue effectively.