P0700high severityDo not driveP0700 Code: Transmission Control System Malfunction
Written in plain English and reviewed by the eli5cars editorial team · Last reviewed June 2026
What it means in plain English
P0700 is not a diagnosis — it's a notification. Your transmission has its own computer (the TCM, transmission control module), and that computer logged its own internal fault code. P0700 is the powertrain system's way of saying 'hey, the transmission computer has a problem — go read its specific codes.' You need a more capable scanner that can talk directly to the TCM to pull the actual sub-code, which will start with P07xx or P08xx. P0700 by itself tells you almost nothing except 'start here.'
⛔ Do not drive with this code active
This fault can cause immediate mechanical or safety damage. Have the vehicle towed or inspected before driving.
Most likely causes — ranked
#1 Transmission solenoid fault (most common sub-code trigger — P0750–P0775 range)
most likelyFix: Transmission solenoids control fluid flow through the hydraulic circuit to engage different gears. A faulty solenoid (bad resistance, stuck open/closed) sets a TCM fault that triggers P0700. Sub-codes like P0750 (Shift Solenoid A) or P0756 (Shift Solenoid B Performance) tell you which solenoid. On many vehicles the solenoids are accessible inside the transmission pan — a valve body or solenoid pack replacement at a shop.
#2 Low or contaminated transmission fluid
likelyFix: Low fluid level or burnt transmission fluid changes hydraulic pressure, causes heat, and can trigger multiple TCM faults. Check transmission fluid level and condition. Fresh, pink/red fluid that smells normal is good. Dark brown, black, or burnt-smelling fluid means a fluid change is overdue. A drain-and-fill with the correct OEM-spec fluid is the first low-cost intervention.
#3 Transmission input or output speed sensor failure
possibleFix: Speed sensors tell the TCM how fast the input shaft (from the engine) and output shaft (to the wheels) are spinning. If they disagree by too much or one goes dead, the TCM logs a fault and triggers P0700. Sensors are typically accessible externally on the transmission case — often a 1-bolt replacement.
#4 Transmission control module (TCM) internal failure
possibleFix: The TCM itself can fail — usually due to heat, moisture ingress, or a wiring short that damages the electronics. Before replacing the TCM, rule out all wiring and sensor causes. A dealer or transmission specialist shop with the OEM scan tool is the right resource for diagnosing TCM failures.
Check engine light on? Get a free code scan
If your check engine light is on, most auto-parts stores (AutoZone, O'Reilly, Advance) will read the code for FREE — no purchase required, just walk in. Bring the code back here and look it up at eli5cars.com/obd2 for the plain-English explanation.
Note: a scan only helps when there's an active fault code. For purely mechanical symptoms (noises, vibrations, leaks), a scan may show nothing — the suspects listed above are your starting point.
Want to read the codes yourself?
First, the free option: AutoZone, O’Reilly, and Advance Auto Parts read your codes for free — no purchase needed. That’s the cheapest way to get the code to look up here. If you’d rather have your own so you can check anytime (and clear a code after a fix), the Veepeak OBDCheck BLE is an inexpensive, reliable plug-in reader that pairs with a free phone app and works on any car sold since 1996.
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Frequently asked questions
Can I drive with a P0700 code?
Probably not safely for long. Many vehicles with P0700 enter a limp mode — limited to one or two gears, reduced power, and no upshifts — to protect the transmission from damage. Drive it only as far as the nearest shop or parts store for diagnosis. Continuing to drive in limp mode for extended distances can cause further transmission damage.
A basic OBD2 scanner only shows P0700. How do I get the real code?
P0700 is a generic code that the engine control module sets to mirror a TCM fault. The actual specific code lives in the TCM's own memory. You need a bi-directional scanner capable of reading transmission-specific codes — either a dealer-level scan tool or a professional aftermarket scanner (Snap-on, Autel, Launch). AutoZone's basic handheld may not pull TCM codes; ask them specifically to check transmission codes.
What does it cost to fix P0700?
It depends entirely on the root cause, which you won't know until you pull the specific sub-code. A fluid change is $150–$250. A solenoid or sensor: $200–$500. A valve body: $500–$1,200. A TCM replacement: $500–$1,500. A full transmission rebuild: $1,800–$4,000. Get the specific TCM sub-code before authorizing any repairs.
Can dirty transmission fluid really cause P0700?
Yes. Contaminated fluid changes viscosity and affects hydraulic pressure throughout the transmission. Pressure sensors and solenoids read out of spec, triggering TCM faults. A drain-and-fill with fresh OEM-spec fluid is always worth trying first on high-mileage vehicles if the fluid looks dark or burnt — it costs $150 at a shop and sometimes resolves codes without further work.