P1700

What Does Code P1700 Mean?

This Diagnostic Trouble Code (DTC) P1700 typically signifies a Transmission Indeterminate Failure, often indicating the Powertrain Control Module (PCM) or Engine Control Module (ECM) has received a request from the Transmission Control Module (TCM) to illuminate the Malfunction Indicator Lamp (MIL). Unlike specific transmission component codes, P1700 does not pinpoint a particular sensor, solenoid, or mechanical failure. Instead, it serves as a general fault notification from the TCM to the PCM, indicating that the TCM has detected a condition severe enough to warrant driver notification, but without a more specific DTC readily available to the PCM from the TCM’s direct diagnostics. In essence, the TCM identifies a significant anomaly within the transmission’s operation, control, or a failure to achieve or maintain a commanded state (such as Neutral), and communicates this general fault to the PCM. The subsystem directly affected is the transmission’s electronic control system and its communication integrity with the powertrain control unit. This code often accompanies other, more specific manufacturer-defined transmission codes stored within the TCM, which an advanced diagnostic tool capable of communicating with the TCM directly can retrieve.

Common Symptoms

• Illumination of the Malfunction Indicator Lamp (MIL) on the dashboard.
• Transmission entering “limp mode,” characterized by restricted gear selection (e.g., stuck in 2nd or 3rd gear) to prevent further damage.
• Harsh or erratic shifting, delayed engagement, or complete loss of specific gears.
• Inconsistent or complete lack of transmission engagement, feeling like the transmission is slipping excessively or completely disengaged.
• Absence of specific gear selections when attempting to shift manually (if applicable).
• Reduced fuel economy due to improper gear ratios.
• Audible noises from the transmission, such as whining, grinding, or clunking during operation or shifting attempts.

What Causes the Code P1700?

• Internal Transmission Mechanical Failure: This is a broad category encompassing worn clutch packs, damaged planetary gears, failed torque converter, or issues with valve body components that prevent proper hydraulic function.
• Faulty Transmission Control Module (TCM): A defective TCM itself can erroneously request the MIL or fail to properly control the transmission’s functions, leading to perceived “indeterminate failure.”
• Malfunctioning Transmission Solenoids or Sensors: While P1700 is general, underlying issues with shift solenoids, pressure control solenoids, turbine speed sensors, or output shaft speed sensors can trigger the TCM to set P1700 if their specific fault codes are not communicated or if the TCM interprets the sensor data as an indeterminate failure.
• Wiring Harness or Connector Issues: Damaged, corroded, or loose wiring and connectors between the TCM, PCM, and various transmission sensors/solenoids can disrupt communication or power supply, leading to erratic operation and the setting of P1700.
• Low or Contaminated Transmission Fluid: Insufficient fluid levels or severely degraded/contaminated fluid can lead to hydraulic pressure issues, overheating, and mechanical wear, ultimately causing the TCM to detect operational anomalies.
• PCM/ECM Internal Fault: Though less common, an internal fault within the PCM/ECM preventing proper communication with the TCM or misinterpreting TCM signals could potentially contribute.

How to Diagnose and Troubleshoot

Diagnosing P1700 requires a systematic approach, starting with the understanding that it is often a secondary or general code. A high-quality diagnostic scan tool capable of communicating with all vehicle modules, especially the TCM, is indispensable.

1. Retrieve All DTCs: Connect an OBD-II scanner and check for any other stored, pending, or historical DTCs, particularly those related to the transmission (P07xx series, P08xx series). P1700 frequently accompanies more specific transmission codes stored within the TCM itself. If other codes are present, diagnose and repair those first, as P1700 may clear automatically upon resolution of the primary fault.
2. Check Transmission Fluid Level and Condition: With the engine at operating temperature (and usually running, if specified by the manufacturer), check the transmission fluid level using the dipstick (if equipped) or inspection plug. Inspect the fluid for color (should be reddish, not dark brown or black), odor (should not smell burnt), and presence of metallic debris. Low fluid or severely degraded fluid can cause significant operational issues.
3. Visual Inspection of Wiring and Connectors: Carefully inspect the wiring harness leading to the transmission, the TCM, and the PCM. Look for signs of chafing, cuts, corrosion, or loose connections. Pay close attention to grounds. Disconnect and inspect connectors for bent pins or corrosion.
4. Perform a Thorough Scan Tool Data Analysis:
   • Monitor transmission sensor data (input/output speed, fluid temperature, gear commanded, gear ratio) while driving the vehicle (if safe to do so and not in limp mode). Look for erratic readings or values outside of expected parameters.
   • Check solenoid command and feedback states.
   • Verify proper communication between the PCM and TCM via the CAN bus data stream. Look for communication errors or dropped packets.
5. Check Power and Ground to TCM: Using a digital multimeter (DMM), verify that the TCM receives proper battery voltage and has a solid ground connection. Refer to the vehicle’s wiring diagram for specific pin locations and expected voltage values. Insufficient power or poor ground can cause erratic TCM operation.
6. Test Transmission Solenoids/Sensors (if indicated by other codes or symptoms): If specific shift anomalies are noted or other DTCs point to particular components, further DMM testing of solenoid resistance or sensor voltage outputs might be necessary. Some solenoids can be tested for functionality using bidirectional control via an advanced scan tool.
7. Component Specific Diagnosis: If no obvious external issues are found and P1700 persists without other specific codes, this could point to an internal TCM failure or a complex internal mechanical issue that the TCM cannot specifically identify but knows is wrong. At this point, advanced diagnostics might involve pressure testing the transmission or considering TCM replacement.

Recommended Repairs and Solutions

The resolution for P1700 is entirely dependent on the root cause identified through thorough diagnosis. Since it’s an “indeterminate” code, focus on addressing the underlying issues:

• Transmission Fluid Service: If the fluid is low, contaminated, or burnt, performing a transmission fluid and filter change (or a flush, if recommended by the manufacturer and condition allows) is often the first step. Ensure the correct type and amount of fluid are used.
• Wiring Harness/Connector Repair or Replacement: Repairing damaged wires, cleaning corroded connectors, or replacing sections of the harness as needed will restore proper electrical communication and power.
• Transmission Solenoid Replacement: If specific shift solenoids or pressure control solenoids are identified as faulty (often indicated by other specific DTCs or test results), replacement of the affected solenoid or the entire solenoid pack within the valve body is a common repair.
• Transmission Speed Sensor Replacement: If input or output speed sensors are malfunctioning, replacing them can resolve erratic shifting or lack of speed signal.
• Transmission Control Module (TCM) Replacement: If the TCM itself is found to be faulty after ruling out all other possibilities, replacement is necessary. This often requires programming or “flashing” the new TCM with the vehicle’s specific software, which usually needs a factory-level scan tool.
• Internal Transmission Repair or Replacement: In cases of severe mechanical failure (e.g., worn clutch packs, planetary gear damage, torque converter issues), an overhaul of the transmission or complete replacement with a rebuilt or new unit will be required. This is typically the most extensive and costly repair.

Mechanics’ Tips:

• Always prioritize diagnosing any other transmission-related DTCs before focusing solely on P1700. P1700 is often a symptom, not the core problem.
• Verify all grounds. Poor grounds are a frequent but overlooked cause of intermittent electrical faults.
• When replacing transmission components, especially solenoids or valve bodies, always use OEM or high-quality aftermarket parts to ensure compatibility and longevity.
• After any transmission repair, clear all DTCs and perform a test drive to ensure the issue is resolved and to allow the TCM to re-learn shifting parameters. Some transmissions require a specific “fast learn” procedure with a scan tool after component replacement.