Transmission Control System Malfunction
In short
P0700 is not a specific fault by itself — it's a general flag the transmission control module (TCM) sets to turn on the check engine light and tell you there's ANOTHER transmission code stored. To actually diagnose it you need a scan tool that reads TCM/transmission codes (many basic readers only show engine codes), then fix the specific P07xx/P08xx code behind it. It often comes with harsh shifting or 'limp' mode.
Is it safe to drive with P0700?
It depends on the real code behind it. P0700 itself just signals a transmission fault; the car may drop into 'limp mode' (locked in one gear) to protect the transmission, which is drivable at low speed but not ideal. If shifting is harsh, slipping, or stuck, limit driving and diagnose the specific stored code before damage accumulates.
Symptoms
- Check engine light on (set by the TCM)
- Harsh, delayed, or erratic shifting
- Transmission stuck in one gear (limp mode)
- Slipping or flaring between shifts
- No obvious symptom in some cases — just the light plus a stored trans code
Common causes (most → least likely)
How to diagnose it (before buying parts)
- 1 Use a scan tool that reads TRANSMISSION (TCM) codes, not just generic engine codes. P0700 alone tells you nothing — you must retrieve the companion P07xx/P08xx code it's pointing to.
- 2 Check the transmission fluid level and condition first (where a dipstick exists): low or burnt fluid causes a wide range of trans faults and is the cheapest thing to rule out.
- 3 Look up the specific underlying code and diagnose THAT — P0700 is just the 'see the other code' flag.
- 4 Inspect the transmission harness connector and grounds for corrosion or damage, a common cause of electronic trans faults.
- 5 Clear codes after repair and road-test through all gears to confirm the underlying code doesn't return.
Repair options & cost
By manufacturer
On CVT-equipped models, P0700 often accompanies CVT-specific codes and judder complaints; check for CVT fluid condition and known extended-warranty coverage before major repairs.
Frequently solenoid or fluid-related; the underlying code (e.g. solenoid pack) is usually the real story. Use the correct ATF spec.
Underlying solenoid and TCM/wiring codes are common. A capable scan tool is essential, as basic readers won't show the companion code.
Check fluid and shift-solenoid codes; some models need a relearn after solenoid or TCM work. The specific stored code drives the repair.
Frequently asked questions
What does P0700 mean exactly?
It's a general 'transmission control system' flag the TCM uses to turn on the check engine light and tell you there's another, more specific transmission code stored. P0700 is the pointer; the companion code is the actual fault.
Why can't my code reader tell me more?
Many inexpensive readers only pull generic powertrain/engine codes. Transmission (TCM) codes live in a separate module, so you need a scan tool that reads transmission codes to see the specific fault behind P0700.
Can I drive with P0700?
Maybe, but carefully. The car may enter limp mode (one gear only) to protect itself. If shifting is harsh, slipping, or stuck, limit driving and get the underlying code diagnosed before further damage.
What's the cheapest thing to check first?
Transmission fluid level and condition. Low or burnt fluid causes many transmission faults, and it's far cheaper to address than solenoids, a TCM, or internal repairs.