Transmission · Powertrain · generic (SAE-defined)
P0700: Transmission Control System (MIL Request)
P0700 means the transmission control module (TCM) has stored one or more of its own fault codes and asked the engine computer to turn on the check engine light.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0700 sets
On many vehicles the transmission is managed by a separate transmission control module (TCM). When the TCM detects a fault that affects emissions, it sends a request to the powertrain control module (PCM), which then stores P0700 and lights the malfunction indicator lamp (MIL). P0700 itself is only a flag; the specific fault lives in the TCM's own code memory, which a basic generic code reader may not be able to access.
Common causes of P0700
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Any transmission fault stored in the TCM
- Transmission speed sensor or range sensor faults
- Shift or pressure control solenoid faults
- Low or degraded transmission fluid causing slip codes
- Wiring or connector problems at the transmission
- TCM fault or communication problem
P0700 symptoms
- Check engine light on
- Transmission stuck in one gear or limp mode
- Harsh, delayed or erratic shifts
- Slipping or flare between gears
- Sometimes no symptoms other than the light
How P0700 is diagnosed
- Use a scan tool that can read the transmission module and retrieve its stored codes
- Record freeze frame data from both the PCM and TCM
- Check transmission fluid level and condition using the manufacturer's procedure
- Diagnose the specific TCM code following its own test procedure
- Inspect the transmission harness and connectors for damage or fluid intrusion
- Check for TCM software updates and service bulletins
Typical fixes for P0700
- Repair the fault identified by the TCM's stored codes
- Correct the fluid level or service the fluid with the specified type
- Repair transmission wiring or connectors
- Update or replace the TCM if it is faulty
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Related codes & warning lights
P0700 FAQ
What does code P0700 mean?
P0700 means the transmission control module (TCM) has stored one or more of its own fault codes and asked the engine computer to turn on the check engine light. The standard definition is "Transmission Control System (MIL Request)."
Can I drive with a P0700 code?
Possibly, but treat it as urgent. The real fault is stored in the transmission module and may involve slipping or limp mode, so drive gently and only until the underlying code is read and addressed.
Why does my code reader only show P0700?
Many basic readers only see the engine computer's codes. The detailed transmission codes are stored in the TCM, so a scan tool that can communicate with that module is needed.
Should I clear P0700 and see if it comes back?
Clearing it removes useful information. Read and record the TCM's codes first, because the underlying fault is what needs to be repaired.
Keep researching
More transmission codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.