P0864

TCM Communication Circuit Range/Performance

Q: Is it safe to drive with P0864?

Short trips may be okay, but a communication fault can put the transmission into limp mode with limited gears. Avoid long or high-speed drives until it's fixed.

Q: Can I just clear P0864?

It usually returns because the communication problem is still present. Check wiring, grounds, and connectors before condemning the module.

Transmission communication (network) Generic OBD-II Medium

What it means

P0864 means the data the transmission control module (TCM) exchanges with the rest of the vehicle is out of range or unreliable — a range/performance problem on the module's communication circuit. The engine still starts, but because the TCM depends on that data to shift, the transmission may shift erratically or fall back to a limp mode with limited gears. Wiring, connectors, and grounds are common causes.

Medium

Can I keep driving? The engine starts, but the transmission may shift erratically or drop into limp mode — drive gently and get it diagnosed before long trips.

Real-world scan data

Seen in

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Delayed, erratic, or missed shifts
Transmission stuck in one gear or in limp mode
Other communication or transmission codes stored alongside it

Common causes

Most likely first

Wiring or connector fault in the TCM communication (bus) circuitLikely
Loose or corroded connectors at the transmission control moduleCommon
Faulty transmission control module (TCM)Common
Fault in another module or the ECM disrupting the busLess often
Electrical interference or a poor ground affecting the signalLess often

How to diagnose & fix

Work through it in order

Scan all modules for communication codes to see whether the fault is TCM-specific or bus-wide.
Inspect the TCM connectors, grounds, and communication wiring for corrosion or damage.
Check power and ground at the TCM, and look for chafed or shorted bus wiring.
Verify TCM software/configuration is correct for the vehicle.
If the circuit is good, have the TCM tested and replaced/reprogrammed as needed. Clear and re-test.

FAQ

Quick answers

Is it safe to drive with P0864?+

Short trips may be okay, but a communication fault can put the transmission into limp mode with limited gears. Avoid long or high-speed drives until it's fixed.

Can I just clear P0864?+

It usually returns because the communication problem is still present. Check wiring, grounds, and connectors before condemning the module.

Read & clear P0864 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX