P0700: Transmission Control System Malfunction Explained
Table of contents
Key Takeaway
P0700 sounds scary but it's just an informational code. Here's what it really means.
P0700 is an informational code only
What P0700 Really Means
P0700 is an informational code only. It tells you the Transmission Control Module (TCM) has stored a fault. The actual fault is a separate, more specific code. See our [OBD-II codes pillar](/codes/) for the full transmission code reference set.
P0700 Is Like a Flag
| What P0700 Is | What P0700 Is Not |
|---|---|
| A flag saying "check transmission codes" | A specific diagnosis |
| Always accompanied by another code | A standalone failure |
| Read by the ECM from the TCM | An engine code |
Common Companion Codes
| Code | Meaning | Severity |
|---|---|---|
| P0715 | Input speed sensor | Medium |
| P0720 | Output speed sensor | Medium |
| P0730 | Incorrect gear ratio | High |
| P0741 | Torque converter clutch stuck | Medium |
| P0750-P0770 | Shift solenoid faults | Medium-High |
STEER reads transmission codes most scanners miss
Most parts-store scanners read only engine codes (ECM). The Transmission Control Module stores its codes separately, and many basic scanners cannot access them. The [STEER OBD-II adapter](/obd2-scanner/) reads both ECM and TCM codes, so the specific fault behind a P0700 — the companion code that tells you what is actually wrong — shows up in the same view. Confirm compatibility on the [compatibility page](/compatibility/).
Frequently Asked Questions
What does P0700 mean on a car?
P0700 is a generic OBD-II code that means "Transmission Control System Malfunction" — but it is informational only. It tells the engine ECM that the separate Transmission Control Module has stored at least one fault. The actual fault is in a companion code (P0715, P0720, P0730, etc.). Without the companion code, P0700 alone tells you almost nothing.
Can I drive with a P0700 code?
Depends entirely on the companion code. If the companion is a sensor fault (P0715, P0720), you can typically drive carefully to a shop. If the companion is a major mechanical issue (P0730 incorrect gear ratio, P0731-P0735 incorrect gear-X ratio), the transmission may be slipping internally and continued driving risks expensive damage. Scan for both engine and transmission codes before deciding.
Why do I have P0700 but no transmission symptoms?
A P0700 with no noticeable shift issues usually means the companion code is a sensor or electrical fault rather than a mechanical problem. The TCM noticed something abnormal but the transmission continued operating in normal mode. Common scenarios are an intermittent speed sensor that returns to function, a momentary solenoid electrical glitch, or an aging shift solenoid that occasionally responds slowly. Read the companion code to confirm.
How do I read the companion code for P0700?
You need a scanner that supports transmission module access (Mode 03 from the TCM, not just the ECM). Many free parts-store scans and basic Bluetooth dongles only read engine codes. Mid-range consumer scanners and shop-level scanners read both. STEER reads TCM codes alongside ECM codes — see the compatibility page for your specific vehicle. Once you have the companion code, the actual fault and repair path become clear.
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