P1693 – Companion DTC Stored: Complete Technical Diagnostic Guide
Technical Definition
OBD-II Code P1693 is a manufacturer-specific diagnostic trouble code that indicates the Powertrain Control Module (PCM) has detected and stored a companion code from another vehicle control module. This code does NOT represent a direct fault in the system, but rather serves as a notification flag that another critical DTC exists in either the Transmission Control Module (TCM) or Engine Control Module (ECM).
P1693 = “Companion DTC Stored in ECM/TCM”
Critical Diagnostic Insight
P1693 is NEVER the root cause of vehicle issues. It is always triggered by a primary fault code in another module. Attempting to repair P1693 directly will result in diagnostic failure and continued vehicle problems.
1.0 Technical Specifications & System Overview
1.1 Control Module Communication Architecture
Modern FCA/Stellantis vehicles utilize a complex network of interconnected control modules that communicate via Controller Area Network (CAN) bus systems. The PCM acts as the primary coordinator for powertrain-related functions, while the TCM and ECM handle specialized subsystems.
| Control Module | Primary Function | Communication Protocol | Typical DTC Range |
|---|---|---|---|
| PCM (Powertrain Control Module) | Overall powertrain coordination, emissions control | CAN-C (High Speed) | P0000-P1899 |
| TCM (Transmission Control Module) | Automatic transmission control, shift scheduling | CAN-C (High Speed) | P0700-P0899 |
| ECM (Engine Control Module) | Engine management, fuel injection, ignition timing | CAN-C (High Speed) | P0100-P0699 |
| BCM (Body Control Module) | Body electrical systems, lighting, accessories | CAN-B (Medium Speed) | B1000-B1999 |
1.2 P1693 Trigger Conditions
The PCM sets Code P1693 when ALL of the following conditions are met:
- A diagnostic trouble code is stored in either the TCM or ECM
- The primary DTC is of sufficient severity to warrant PCM notification
- The PCM’s diagnostic monitor runs and detects the companion code presence
- The ignition cycle counter reaches the threshold for MIL illumination
Technical Note: Freeze Frame Data
When P1693 is stored, the PCM captures “Freeze Frame” data at the moment of detection. This includes engine RPM, vehicle speed, coolant temperature, load percentage, and fuel system status. This data corresponds to the PRIMARY fault, not P1693 itself.
2.0 Related & Companion Error Codes
2.1 Common Primary DTCs That Trigger P1693
| Primary DTC | Description | Module | Typical Causes | Relationship to P1693 |
|---|---|---|---|---|
| P0700 | Transmission Control System Malfunction | TCM | Wiring harness, TCM failure, sensor issues | Direct trigger – P1693 stores as companion |
| P0601 | Internal Control Module Memory Check Sum Error | PCM | PCM software corruption, voltage spikes | Co-occurs with P1693 |
| P0606 | PCM Processor Fault | PCM | PCM hardware failure, internal damage | Primary code with P1693 companion |
| P0841 | Transmission Fluid Pressure Sensor/Switch A Circuit Range/Performance | TCM | Faulty pressure sensor, wiring, low fluid | Triggers P1693 when stored in TCM |
| P0218 | Transmission Fluid Over Temperature Condition | TCM | Overheating transmission, cooler issues | Severe fault triggers P1693 notification |
| U0100 | Lost Communication with ECM/PCM | Multiple | CAN bus faults, module power issues | Network fault may trigger P1693 |
| U0401 | Invalid Data Received from ECM/PCM | TCM/ECM | Communication errors, corrupted data | Data faults trigger companion codes |
2.2 P1693 Code Family Hierarchy
├── P1694 – Manufacturer Control Fuel Air Metering
├── P1695 – Manufacturer Control Auxiliary Emissions Controls
├── P1696 – Manufacturer Control Auxiliary Inputs
└── P1697 – Manufacturer Control Auxiliary Outputs
3.0 Comprehensive Diagnostic Procedure
Safety Precautions
Before beginning diagnosis: Disconnect battery negative terminal, allow PCM capacitors to discharge (5 minutes), use proper personal protective equipment, and ensure vehicle is in park with parking brake engaged.
3.1 Required Diagnostic Equipment
| Tool | Minimum Specification | Purpose | Recommended Model |
|---|---|---|---|
| Scan Tool | J1979 compliant, CAN capable | Reading all DTCs across modules | Autel MaxiCOM, Snap-on MODIS |
| Multimeter | True RMS, 10MΩ impedance | Voltage/resistance measurements | Fluke 87V, Innova 3320 |
| Oscilloscope | 20MHz bandwidth minimum | CAN bus signal analysis | PicoScope 4425, Hantek |
| Wiring Diagrams | Vehicle-specific | Circuit verification | Mitchell1, ALLDATA |
3.2 Step-by-Step Diagnostic Flowchart
Step 1: Initial Code Scan
Connect advanced scan tool to DLC. Perform FULL SYSTEM SCAN across all modules (PCM, TCM, ECM, BCM). Document ALL stored codes, pending codes, and history codes. Note which codes are current vs. history.
PCM: P1693 (Current)
TCM: P0700 (Current), P0732 (History)
ECM: P0123 (Current)
Step 2: Identify Primary DTC
Analyze scan results. Ignore P1693 initially. Identify the CURRENT primary DTC with highest priority (typically transmission or engine codes). P0700 is most common primary with P1693.
Step 3: Access Freeze Frame Data
For each current DTC (including P1693), record freeze frame data. Compare parameters between codes. Mismatched data indicates intermittent issues or different fault events.
Key Parameters: RPM, VSS, ECT, MAP/MAF, Fuel Trim, Load %
Step 4: Diagnose Primary Code
Follow manufacturer-specific diagnostic procedures for the PRIMARY DTC. Use wiring diagrams to verify circuit integrity. Test sensors, actuators, and module communications related to the primary fault.
Example: For P0700, test TCM power, ground, and CAN communication circuits.
Step 5: Clear Codes & Monitor
After repairing primary fault, clear ALL codes from ALL modules. Perform 3 consecutive drive cycles monitoring for code return. Use scanner to monitor live data during test drive.
Drive Cycle Requirements: Cold start, various loads, highway speeds, deceleration events.
Step 6: Final Verification
If codes return, repeat diagnosis with focus on intermittent issues. If no codes return, perform final system check and document repair. Update module software if TSBs exist for the issue.
4.0 Wiring Diagrams & Connector Specifications
4.1 PCM/TCM Communication Circuit (Typical)
PCM Connector C1 (Gray) – Pin 26: CAN Low (Circuit 2500)
TCM Connector (Black) – Pin 12: CAN High (Circuit 2501)
TCM Connector (Black) – Pin 13: CAN Low (Circuit 2500)
Resistance (Terminated): 60Ω between CAN High & Low
Voltage: CAN High = 2.5-3.5V, CAN Low = 1.5-2.5V
4.2 Common Failure Points
| Location | Failure Mode | Symptoms | Test Procedure |
|---|---|---|---|
| C110 Connector (Firewall) | Corrosion, pin tension loss | Intermittent communication loss | Voltage drop test, visual inspection |
| CAN Splice Pack S210 | Poor crimps, oxidation | Multiple module failures | Resistance to ground test |
| TCM Ground G102 | Loose connection, corrosion | Transmission limp mode | Voltage drop < 0.1V to battery negative |
| PCM Power Feed Fuse 22 | High resistance, intermittent | Random resets, memory loss | Current draw test, fuse voltage drop |
Frequently Asked Questions (FAQ)
Answer: It depends entirely on the PRIMARY fault code. If the primary code is for a minor sensor issue, driving may be possible. However, if P1693 is accompanied by transmission codes (P0700 series) or severe engine codes, the vehicle may be in limp mode with limited functionality. Always diagnose the primary code before determining drivability.
Answer: P1693 returns because the PRIMARY fault has not been repaired. Clearing codes only removes the symptom, not the cause. The companion code will reappear within 1-3 drive cycles because the PCM continues to detect the underlying issue in the TCM or ECM.
Answer: P1693 indicates a companion code stored from TCM/ECM. P1694 indicates a companion code related specifically to fuel and air metering systems. Both are companion codes, but P1694 points to a more specific subsystem issue.
Answer: Yes. Basic code readers often only show P1693. You need a professional-grade scanner capable of accessing ALL modules (PCM, TCM, ECM) to see the primary codes. Look for scanners with “bi-directional control” and “module communication” capabilities.
Answer: Indirectly, yes. Low voltage or voltage spikes can cause module communication errors, which may trigger primary codes in TCM/ECM, which then trigger P1693. Always verify battery state of charge (>12.4V) and charging system function before module diagnosis.
Answer: There’s no fixed cost for P1693 because it depends on the primary fault. Diagnosis alone typically costs $120-$250. Repairs range from $150 (sensor replacement) to $2,000+ (TCM replacement or transmission repair). The P1693 code itself adds no additional repair cost.
