OBD-II Diagnostic Trouble Code
P0700 — Transmission Control System Malfunction
P0700 is an informational code set in the engine ECM when the transmission control module (TCM) has stored its own fault and requested the malfunction indicator light. It does not identify a specific transmission problem by itself; the TCM codes must be read, whether the truck has a conventional automatic or an automated manual.
Severity 4/5
Truck-relevant
Stop within 50 mi
Severity
Stop within 50 mi
Transmission Control System Malfunction
Code
P0700
Category
Powertrain
Subsystem
Transmission
Truck-relevant
Yes
What this means for truckers
P0700 — see existing entry.
Before you replace parts — try this first
P0700 on the Transmission system is most often stored tcm fault such as a speed sensor, solenoid or ratio code — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Check-engine light, often with the transmission in limp or fail-safe mode (locked in one gear, harsh or no shifts), a flashing or blank shift display, or no obvious drivability change. Symptoms depend entirely on the underlying TCM fault.
Common causes
- CommonStored TCM fault such as a speed sensor, solenoid or ratio code ($100–$1500)
- CommonLow or degraded transmission fluid causing pressure or ratio faults ($100–$600)
- OccasionalWiring or connector problem at the transmission or TCM ($150–$700)
- OccasionalInternal transmission failure ($3000–$10000)
- RareTCM failure ($800–$2500)
How to fix
Read codes from the TCM with a scan tool capable of transmission diagnostics
When to use: Always first; P0700 alone does not identify the fault
Check transmission fluid level and condition
When to use: Before deeper diagnostics
Diagnose the specific TCM code following its procedure
When to use: Once TCM codes are known
Clear codes and road test to confirm
When to use: After repair
Affects most
- GMC Sierra 35003 complaints mention this code
- Chevrolet Silverado 35001 complaint mention this code
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P0701 — Transmission Control System Range/Performance
- → P0702 — Transmission Control System Electrical
- → P0703 — Brake Switch B Circuit
- → P0705 — Transmission Range Sensor Circuit Malfunction
- → P0706 — Transmission Range Sensor Circuit Range/Performance
- → Complaints on GMC Sierra 3500
- → Complaints on Chevrolet Silverado 3500
Frequently Asked Questions
Can I drive with code P0700?
Drive with caution. P0700 is severity 4 — stop within ~50 miles. Most commercial diesel codes at this severity (turbo, fuel rail, transmission solenoid) can damage adjacent expensive components if left unrepaired. Get to a service location before highway-speed loads.
How much does it cost to fix P0700 on a commercial truck?
Total repair cost ranges $100–$10000 depending on the root cause. The cheapest fix is usually the first one listed below — Stored TCM fault such as a speed sensor, solenoid or ratio code — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P0700 fail a DOT inspection?
P0700 typically doesn't fail an inspection on its own. Inspectors focus on safety items (brakes, steering, tires, lights, HOS). Transmission codes only become an issue if the truck has shifting problems severe enough to qualify as 'mechanical fitness' OOS. Fix to prevent escalation.
What's the difference between P0700 and related codes?
P0700 is closely related to: P0701 (Transmission Control System Range/Performance), P0702 (Transmission Control System Electrical), P0703 (Brake Switch B Circuit), P0705 (Transmission Range Sensor Circuit Malfunction). These codes share the same subsystem (transmission) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P0700 is set without the companions, the issue is more isolated.
How do I prevent P0700 from coming back after a repair?
For P0700 (Transmission Control System Malfunction), prevention centers on the transmission system. Service transmission fluid at the OEM interval (typically 150K–250K miles for HD autos). Don't skip the magnet/strainer inspection. After repair, perform an adaptive shift relearn with a scan tool (or drive 40+ miles for adaptive ECMs to relearn naturally).