P0700 on GMC
Transmission Control System Malfunction
P0700 on GMC vehicles indicates transmission control system malfunction. Au7o has documented this code across 5 GMC models — most commonly on C/K 1500, Sierra 1500, Sierra 2500HD. P0700 is a general code indicating the transmission control module (TCM) has detected a fault somewhere in the transmission control system and has requested the check engine light be turned on. By itself it doesn't pinpoint the problem — it's an 'umbrella' code that tells you to look for additional, more specific transmission codes stored alongside it. The actual fault could be electrical, a sensor, a solenoid, or an internal transmission issue. You may notice harsh or delayed shifts, slipping, or the transmission going into a protective 'limp' mode. Typical repair costs on GMC range from $300 to $6,500, depending on the specific model and root cause.
Common Causes of P0700
- •Stored companion transmission codes pointing to the real fault
- •Faulty shift solenoid or pressure control solenoid
- •Low, dirty, or degraded transmission fluid
- •Faulty transmission speed or input/output sensor
- •Wiring, connector, or ground problems at the transmission
- •Failing transmission control module (TCM)
- •Internal transmission mechanical wear or clutch problems
- •Valve body fault or sticking valves
P0700 on GMC by Model
GMC C/K 1500(1 issue)
- 4L60E Automatic Transmission Failure1993-1998
Same 4L60E transmission issues as Chevrolet C/K. Sun shell failure, 3-4 clutch pack burnup, and worn input drum.
GMC Sierra 1500(2 issues)
- 10L80/10L90 10-Speed Valve Body Failure — Loss of Reverse, Limp Mode, and Year-Long Parts Backorder2024-2025
2024-2025 Sierra 1500 trucks with the 10-speed automatic (5.3L L84, 6.2L L87 and 3.0L Duramax LZ0) are failing at very low mileage with a stuck valve-body solenoid. Symptoms: a 'Service Transmission' or 'Service Transmission — Unable to Shift Soon' message, sudden hard/slamming shifts, slipping, complete loss of reverse (owners have had to push the truck out of parking spaces), and default limp operation limited to fifth gear and reverse. Several complaints report the failure occurring under 7,000 miles. NHTSA reports cite DTC P2818 (pressure control solenoid) and P0747/P0700. The situation is compounded by a national valve-body backorder — owners document 50-plus days and in some cases over a year waiting for the part, with GM sometimes authorizing a full transmission replacement instead. Complaint ODI numbers include 11756150, 11754176, 11748050, 11744152, 11739083, 11727368, 11721983, 11694617, 11684139, 11680422, 11680435, 11654431, 11644523, 11634982 (2024) and 11711937 (2025).
- P0700 — Transmission Fault Flag from Failing 6L80/6L90 Internal TEHCM2007-2018
P0700 itself is only a flag: the Transmission Control Module has stored one or more transmission faults and is requesting the MIL. On Sierra 1500s with the 6L80 (and 6L90 on heavier variants) 6-speed automatic, the notable design issue is that the TCM is integrated into the valve body as a TEHCM (transmission electro-hydraulic control module), bolted inside the pan and sitting in 180-250°F fluid. Repeated heat cycling degrades the module and its integrated pressure switches and solenoids. When the TEHCM or a shift/pressure-control solenoid begins to fail, it sets specific sub-codes (e.g., P2534, P0742, P0761) plus the umbrella P0700, and the truck can exhibit harsh or missed shifts, slipping, or limp mode. Critically, on the 6L80/6L90 the solenoids are over-molded into the non-serviceable TEHCM and generally can't be replaced individually.
GMC Sierra 2500HD(1 issue)
- Allison 1000/2000 Transmission TCM Failure and Harsh Shifting2011-2025
The Allison 1000 (gas) and Allison 2000 (diesel) 6-speed automatic transmissions used in Sierra 2500HD/3500HD are widely regarded as extremely durable, but the Transmission Control Module (TCM) and solenoid pack do develop faults. Common issues include harsh 1-2 shifts, transmission sticking in one gear, slip codes, and the truck going into limp mode (3rd gear only). The Allison's proprietary Transynd fluid is critical — using non-approved fluid is the leading cause of premature solenoid wear. TCM software updates from GM address most calibration-related shift complaints.
GMC Sierra 3500HD(1 issue)
- Allison 1000 Transmission Control Module and Sensor Failures2008-2019
The Allison 1000 transmission paired with the Duramax diesel in 2008-2015 Sierra 3500HD trucks has a high failure rate for the Transmission Control Module (TCM). A class action suit was filed covering these years. Additional issues include input/output speed sensor failures causing no-forward/reverse conditions, and certain 2012 trucks built with incorrect thrust bearings.
GMC Yukon(1 issue)
- 10L80 10-Speed Transmission Harsh Shifting, Shudder and Rear-Wheel Lock-Up2021-2023
NHTSA campaign 24V797 covers certain 2021 diesel GMC Yukon vehicles. A transmission control valve can fail and cause the rear wheels to lock.
Looking for P0700 on a different make?
View P0700 across all makes →Frequently Asked Questions
What does P0700 mean on GMC?▼
P0700 stands for "Transmission Control System Malfunction." P0700 is a general code indicating the transmission control module (TCM) has detected a fault somewhere in the transmission control system and has requested the check engine light be turned on. By itself it doesn't pinpoint the problem — it's an 'umbrella' code that tells you to look for additional, more specific transmission codes stored alongside it. The actual fault could be electrical, a sensor, a solenoid, or an internal transmission issue. You may notice harsh or delayed shifts, slipping, or the transmission going into a protective 'limp' mode. On GMC specifically, this code is documented across 5 models.
What causes P0700 on GMC vehicles?▼
Common causes on GMC: Stored companion transmission codes pointing to the real fault, Faulty shift solenoid or pressure control solenoid, Low, dirty, or degraded transmission fluid, Faulty transmission speed or input/output sensor, Wiring, connector, or ground problems at the transmission. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0700 on a GMC?▼
Repair costs on GMC range from $300 to $6,500, depending on the specific model and root cause.
Which GMC models have P0700 documented?▼
Au7o has documented P0700 on 5 GMC models: C/K 1500, Sierra 1500, Sierra 2500HD, Sierra 3500HD, Yukon.