Number P0700: Transmission Control System (MIL Request)
P0700 is a notice code: the separate transmission control module has stored an emission-related fault of its own and asks the engine module to switch on the check engine light. The actual fault – a sensor, solenoid, ratio or speed sensor code – is stored in the transmission module and must be read w
Can you drive with P0700?
Severity: Fix promptly. Usually yes for short trips if it shifts and pulls normally. Slipping, banging shifts or a refusal to move means tow it.
If you ignore it: Transmission faults compound: contaminated fluid and slipping clutches wear fast, and a repairable valve-body issue becomes a full rebuild.
This is the #44 most common code in our top-150 library, in the transmission family (Powertrain system). Severity is Number Nest's editorial triage — if the light is flashing or the car feels unsafe, stop driving it whatever any page says.
What P0700 means
P0700 is a notice code: the separate transmission control module has stored an emission-related fault of its own and asks the engine module to switch on the check engine light. The actual fault – a sensor, solenoid, ratio or speed sensor code – is stored in the transmission module and must be read with a tool that can address it; simple OBD readers often show only P0700. GM's engine module reads the request message from 3 s after start; Subaru-based systems (Saab 9-2X) light the MIL at once and clear it after three fault-free cycles. Ford's engine modules with integrated transmission control do not use P0700. Any limp mode comes from the transmission fault, not from P0700.
Systems involved: transmission control module, engine control module (ECM/PCM), can bus.
Causes, ranked by likelihood
| # | Cause | Likelihood |
|---|---|---|
| 1 | Actual fault stored in the transmission module (sensor, solenoid, ratio, speed sensor) | most likely |
| 2 | Wrong transmission fluid level or condition causing slip or ratio codes | possible |
| 3 | Harness or connector at the transmission corroded or damaged | possible |
| 4 | Low system voltage or weak battery | less common |
| 5 | Transmission module or software faulty | less common |
Check them in order — the list is ranked so the likely, cheaper causes come before the expensive part.
Symptoms you may notice
- Check engine light, possibly transmission warning
- Depending on the transmission fault: limp mode, harsh or delayed shifts
- Often no symptoms if the fault was intermittent
- Simple OBD reader shows only P0700
Misdiagnosis traps
- P0700 alone is a doorbell, not a diagnosis: it only says the transmission computer has codes. Replacing parts without reading the transmission codes behind it is pure guessing.
- Low system voltage from a dying battery sets transmission codes on many cars — test the battery before the gearbox.
How a good shop confirms it
- Read the transmission controller's own codes with a scan tool that can; check fluid level/condition and battery health.
Repair options & costs
| Repair | Shop total (parts + labor) | DIY (parts only) | Difficulty |
|---|---|---|---|
| Transmission shift solenoid | $338 – $838 | $150 – $400 (parts only) | 4/5 |
National ranges from Number Nest's cost model (midsize car, independent shop, US-average labor).
OBDex repair data for this code rates the job difficulty medium with a typical labor time in the 0.5–6 hour range and DIY possible: see the guide above.
Price this repair in your state
Estimated total: — (midsize car, independent shop)
Frequently asked questions
Is P0700 safe to drive on?
It depends entirely on the code behind it — some are minor solenoid faults, some are early warnings of major failure. Getting the underlying code read promptly is the safe move.
How much does it cost to fix P0700?
The fix most associated with this code — transmission shift solenoid — runs $338 – $838 at an independent shop for a midsize car in our cost model (parts + labor, US average). The code names a system, not a part, so confirm the cause before spending: the ranked causes above are ordered by likelihood.
Can I drive with P0700?
See the can-you-drive verdict above — it is based on the system involved and the cascading-damage risk, and it is our editorial triage, not a manufacturer instruction. If the light is flashing or the car feels unsafe, stop driving it regardless of any code.
Will P0700 clear itself?
If the fault was a one-off (a loose cap, a cold-start glitch), the light can go out after several clean trips and the code ages into history. A fault that is still present re-sets the code as soon as the car runs that self-test again — monitors run under specific conditions, which is why "it hasn't come back in two days" is not proof of a fix.
Will my car fail inspection with P0700?
In states with OBD-based emissions inspection, yes — an illuminated check-engine light or an incomplete readiness monitor fails the test regardless of what the tailpipe would show. C-codes (ABS) fall under safety inspection instead in states that have one.
What should I check first for P0700?
The first item on the ranked-causes list above — it is ranked likelihood-first for exactly this reason — plus the free checks: recent work in the area (connectors left loose are a classic), fluid levels, and the battery and grounds on electrical codes.
Where this data comes from
Code facts, causes and symptoms come from OBDex — an open dataset of independently authored descriptions of the standardized generic OBD-II codes (CC0 1.0, public domain; github.com/foerbsnavi/OBDex). The SAE J2012 document itself is copyrighted and is not reproduced here. Cost ranges are Number Nest's own US planning model: national parts and labor ranges cross-checked against the CarMD Vehicle Health Index 2026 published averages, with labor adjustable by the BLS OEWS May 2025 state wage index for auto technicians (occupation 49-3023) — a wage index, not a surveyed shop rate. Severity and can-you-drive notes are our editorial triage, not a manufacturer instruction.