The P0861: Gear Shift Module Communication Circuit Low refers to an issue where the communication circuit between the gear shift module and other vehicle systems is detecting lower-than-expected voltage. This can lead to transmission malfunctions or improper shifting. The problem could arise from faulty wiring, a malfunctioning gear shift module, or transmission control module (TCM) issues.
P0861 – Quick Overview
| Code | Information |
|---|---|
| Meaning | P0861: Gear Shift Module Communication Circuit Low |
| Is it serious? | Yes, this can cause improper gear shifting and transmission issues. |
| Possible causes | – Low voltage in the gear shift module communication circuit – Faulty module or wiring – Faulty transmission control module (TCM) |
| How to diagnose? | – Test the circuit for low voltage – Inspect wiring and connectors – Replace faulty components if needed |
P0861 Meaning
The P0861: Gear Shift Module Communication Circuit Low code indicates that the voltage in the communication circuit between the gear shift module and the vehicle’s control systems is below the expected range. This can result in improper communication, which may cause the transmission to malfunction, preventing proper shifting.
Step-by-step diagnostic guide
| Action | Description | Tools Needed |
|---|---|---|
| Check for Other Codes | Use an OBD-II scanner to check for additional communication-related or transmission codes. | OBD-II Scanner |
| Inspect Gear Shift Module | Visually inspect the gear shift module for any signs of damage, wear, or loose connections. | Flashlight, Safety Gloves |
| Test the Circuit for Low Voltage | Use a multimeter to measure the voltage in the gear shift module communication circuit and ensure it falls within manufacturer specifications. | Multimeter |
| Check Wiring and Connectors | Inspect the wiring and connectors for damage, corrosion, or loose connections that could cause low voltage in the circuit. | Flashlight, Multimeter |
| Replace Faulty Components | If the gear shift module, wiring, or connectors are faulty, replace the necessary components to restore proper communication voltage. | Replacement Parts, Basic Tools |
| Clear the Code and Test Drive | After repairs, clear the code using an OBD-II scanner and take the vehicle for a test drive to ensure proper transmission function. | OBD-II Scanner, Vehicle Owner’s Manual |
| Recheck for Codes | After the test drive, re-scan the system to confirm that the P0861 code does not return. | OBD-II Scanner |
Free PDF: How to choose OBD2 scanner
I’ve made you a free PDF to choose the OBD2 scanner in 5 minutes.
✅ Which OBD2 scanner is best?
✅ Which type should you get (DIY, Pro, Hobby)
✅ What is the best scanner for the exact brand/feature (e.g best for BMW)
✅ How to get a Bi-Directional tool for as cheap as $40
✅ Discount coupons for scanners
PDF is 100% free and it is designed to help you pick a scanner in less than a few minutes! Not a boring 50-page guide.
Just tell me where to send it.
Hi, I am Juraj “Yuri” Lukacko. I got frustrated by unhelpful and scammy mechanics, so I decided to learn everything about car diagnostics myself. I test dozens of new car diagnostic tools every month along with learning new strategies to fix and customize cars. About Juraj Lukacko (Yuri)