1. What is the P0802 Code?
The Diagnostic Trouble Code (DTC) P0802 is a generic powertrain code applicable to many OBD-II vehicles (1996 and newer), including Chevrolet, Kia, GMC, Dodge, Ford, Ram, etc.
This code indicates that the Powertrain Control Module (PCM) has received a signal from the Transmission Control System (TCS) reporting a malfunction that requires the Malfunction Indicator Lamp (MIL) to be illuminated.
2. Transmission System Operation
The Transmission Control Module (TCM) can be a standalone unit or integrated into the Engine Control Module (ECM), forming the PCM.
The PCM regulates the transmission using various sensors to control the hydraulic fluid and pressure needed for shifting gears. It relies particularly on:
- Electronic Pressure Control (EPC) Solenoids: Regulate fluid pressure.
- Electronic Pressure (EP) Sensors: Provide information on fluid pressure.
- Electronic Shift Solenoids: Control fluid flow to allow gear changes.
- Transmission Input and Output Speed Sensors: Verify the effectiveness of gear shifting.
3. Severity of the P0802 Code
A P0802 code indicates a potentially serious issue with the TCS. It is recommended to diagnose and repair the fault quickly to avoid further damage to the transmission.
4. Symptoms of the P0802 Code
Possible symptoms include:
✅ Irregular or harsh shifting
✅ Delayed or no gear engagement
✅ Transmission entering “limp mode”
5. Common Causes of the P0802 Code
Possible causes include:
🔴 A faulty PCM or TCM module
🔴 Open or shorted transmission control circuits
🔴 Controller programming error
6. Troubleshooting Steps for the P0802 Code
🔍 Step 1: Checking Transmission Fluid
✔️ Ensure the transmission fluid is clean and at the proper level.
✔️ If there is a leak, locate and repair it before refilling with the recommended fluid.
✔️ If the fluid is dark and smells burnt, it should be replaced (drain and filter change recommended).
🔍 Step 2: Using an OBD-II Scanner
✔️ Connect an OBD-II scanner to retrieve stored codes and freeze frame data.
✔️ Note this information before clearing the codes.
✔️ Perform a road test to see if the code resets.
🔍 Step 3: Analyzing Circuits and Sensors
✔️ Consult the vehicle’s electrical diagrams to identify TCM/PCM connections.
✔️ Check voltages and grounds at the TCM/PCM using a digital voltmeter (DVOM).
✔️ Test components involved in the observed symptoms.
🔍 Step 4: Checking Fuses and Circuits
✔️ Test TCM/PCM circuit fuses under load to avoid diagnostic errors.
✔️ Check circuit resistance by disconnecting controllers before testing with the DVOM.