Fix P2784: STEP-BY-STEP diagnostic GUIDE!

The P2784: Input/Turbine Speed Sensor ‘A’/’B’ Correlation code indicates that the readings from input/turbine speed sensors ‘A’ and ‘B’ do not match as expected. This discrepancy could be caused by a faulty speed sensor, damaged wiring, or issues within the control module that monitors these sensors. Accurate readings from these sensors are crucial for the transmission control module to manage gear shifts properly.

P2784 – Quick Overview

Code	Information
Meaning	P2784: Input/Turbine Speed Sensor ‘A’/’B’ Correlation
Is it serious?	Yes, mismatched sensor readings can cause improper transmission operation, resulting in harsh shifting, slipping, or a failure to change gears appropriately, which may impact drivability and transmission health.
Possible causes	– Mismatch between input/turbine speed sensor ‘A’ and ‘B’ – Faulty sensors or wiring – Control module issues
How to diagnose?	– Compare readings from input/turbine speed sensor ‘A’ and ‘B’ – Inspect wiring and connectors – Verify control module functionality – Replace faulty sensors or components as needed

P2784 Meaning

The P2784: Input/Turbine Speed Sensor ‘A’/’B’ Correlation code indicates that there is a discrepancy between the readings of input/turbine speed sensor ‘A’ and input/turbine speed sensor ‘B’. These sensors measure the speed of the transmission’s input shaft, and a mismatch can indicate that one or both sensors are not functioning correctly, the wiring between them is damaged, or the control module is misinterpreting their data. When the transmission control module receives conflicting information from these sensors, it can lead to erratic shifting and poor vehicle performance.

Step-by-step diagnostic guide

Action	Description	Tools Needed
Check for Other Codes	Use an OBD-II scanner to identify if there are any other related codes. Additional codes might provide insight into which sensor or other transmission components are causing the correlation issue.	OBD-II Scanner
Compare Readings from Input/Turbine Speed Sensors ‘A’ and ‘B’	Use a diagnostic tool to monitor and compare the output readings from both input/turbine speed sensors ‘A’ and ‘B’. Look for any significant differences or inconsistencies in their values, especially during acceleration and deceleration.	Diagnostic Tool, Manufacturer Specifications
Inspect Wiring and Connectors	Perform a visual inspection of the wiring and connectors associated with sensors ‘A’ and ‘B’. Look for damaged or corroded wires, loose connectors, or poor contacts that could result in erratic or incorrect sensor signals. Properly secure and repair any faulty wiring or connectors.	Flashlight, Safety Gloves
Check for Continuity and Shorts	Use a multimeter to test for continuity in the wiring of both sensors. Look for shorts to power or ground, and confirm that the wires have no open circuits. Poor wiring can lead to discrepancies in sensor outputs.	Multimeter
Test Both Speed Sensors	Remove and test both input/turbine speed sensors individually. Use a multimeter to check their resistance and voltage output against manufacturer specifications. If either sensor is out of specification, replace it to ensure accurate readings.	Multimeter, Manufacturer Specifications
Verify Control Module Functionality	Use a diagnostic tool to verify that the control module is processing the sensor signals correctly. Problems in the control module may cause it to misinterpret the readings from sensors ‘A’ and ‘B’, resulting in the correlation issue. If necessary, update the module’s software or replace it.	Diagnostic Tool, Manufacturer Software
Replace Faulty Sensors or Components as Needed	Replace any faulty components found during testing. This may include speed sensors, connectors, wiring, or even the control module. Ensure that all replacement parts are compatible with the vehicle’s specifications for optimal performance.	Replacement Sensors, Wiring Repair Kit
Clear the Code and Test Drive	Once the necessary repairs are complete, use an OBD-II scanner to clear the P2784 code. Take the vehicle for a test drive, monitoring the input/turbine speed sensor readings to ensure that they correlate correctly and that the transmission shifts smoothly.	OBD-II Scanner
Recheck for Codes	Perform a final scan after the test drive to confirm that the P2784 code has not returned. If the code persists, further diagnostics may be required to identify any remaining issues affecting the correlation between sensors ‘A’ and ‘B’.	OBD-II Scanner