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DTC codes / GM codes / P1700

P1700 · GMTransmission Indeterminate Failure

P1700 on a GM vehicle means the transmission control module (TCM) has detected an internal condition it cannot attribute to a specific sensor or solenoid circuit, so it flags an indeterminate transmission failure. The computer is not pointing to one failed part; it is reporting that its self-checks and rationality tests produced conflicting or out-of-range results that do not match any single defined fault.

SystemPowertrain
Code typeGM specific
SeverityMedium
Fix difficultyProfessional
AreaTransmission

Symptoms you may notice

  • Illumination of the check engine light or transmission warning light, often with no other symptoms besides the warning light
  • Transmission stuck in a default or limp-home gear, usually second or third, with harsh or delayed shifts
  • Erratic shift timing or shuddering during acceleration that does not follow a consistent pattern
  • Reduced fuel economy or higher engine rpm at highway speed because the torque converter clutch may not lock
  • Intermittent loss of power or a brief neutral feel while driving, sometimes accompanied by a stored pending code
  • No drivability complaint at all, with the code appearing only during a scan of stored history

Common causes, most likely first

  1. Low or degraded automatic transmission fluid (ATF) causing erratic hydraulic pressure and confused TCM rationality checks
  2. A failing or contaminated transmission fluid pressure switch or manifold pressure switch assembly sending inconsistent signals
  3. Wiring harness chafing or corrosion at the transmission connector, especially where the loom passes near heat or sharp edges
  4. A weak or failing transmission control module (TCM) or powertrain control module (PCM) with internal fault memory corruption
  5. A sticking or worn shift solenoid or torque converter clutch (TCC) solenoid that does not respond within the expected window
  6. Internal mechanical wear in the valve body or clutch packs that produces pressure and slip values outside the TCM's expected range
  7. A weak battery or poor ground connection causing voltage spikes that disturb TCM self-diagnostics

How to diagnose and fix it

  1. Scan all modules for stored and pending codes, record freeze-frame data, and check for related transmission codes before clearing anything
  2. Inspect the transmission fluid level, color, and smell, and check for leaks or contamination that would explain erratic hydraulic behavior
  3. Visually inspect the transmission wiring harness and connector pins for chafing, corrosion, or loose terminals, and perform a wiggle test while watching live data
  4. Check battery voltage and ground straps, including the engine-to-body and transmission-to-chassis grounds, to rule out electrical noise
  5. Use a scan tool to monitor transmission pressure switch states, solenoid command versus actual response, and slip data during a road test
  6. Perform the manufacturer's pinpoint diagnostic procedure for P1700, which typically includes resistance and voltage checks at the TCM connector
  7. Repair or replace the confirmed faulty component, clear codes, and verify with a relearn or adaptive drive cycle that the code does not return

Why P1700 is rarely a single failed part

  • P1700 is a catch-all rationality code, so technicians who replace the TCM first often find the code returns because the real cause was a chafed wire or low fluid level.
  • A weak battery or failing alternator can set P1700 on GM vehicles because voltage dips during cranking disturb the TCM's internal self-test, and the transmission itself may be perfectly healthy.
  • Fluid pressure switch assemblies on GM transmissions commonly degrade internally and produce intermittent contradictory signals that the TCM interprets as an indeterminate failure rather than a specific switch code.
  • After any transmission repair, the TCM adaptive learning must be reset and a relearn drive cycle completed, or P1700 can reappear simply because the old shift adaptives no longer match the repaired hardware.
  • A loose or corroded ground at the transmission case or engine block can mimic an internal transmission failure, so ground integrity deserves checking before any internal diagnosis.

Can I keep driving with P1700?

You can usually drive the vehicle to a shop if the transmission still engages and shifts, but avoid heavy acceleration, towing, or long highway trips because limp-home mode and harsh shifts can worsen internal wear. If the transmission slips, flares, or drops into neutral while driving, stop and arrange a tow rather than continuing.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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