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Professional Automotive Diagnostic Guides & Technical Resources
P1694 Complete Technical Guide: No CCD/J1850 Bus Message from ECM
1.0 Technical Overview & Code Definition
OBD-II Code P1694 is a manufacturer-specific diagnostic trouble code (DTC) that specifically affects Chrysler Corporation vehicles (Chrysler, Dodge, Jeep, RAM) equipped with the Chrysler Collision Detection (CCD) or J1850 (VPW) multiplexed communication network. This code sets when the Powertrain Control Module (PCM), acting as the network gateway, fails to detect heartbeat messages from the Engine Control Module (ECM) on the CCD data bus for a predetermined timeframe (typically 5-10 seconds).
1.1 Communication Protocol Specifications
- Protocol Type: Chrysler Collision Detection (CCD) – SAE J1850 VPW (Variable Pulse Width)
- Data Rate: 7.8125 kilobits per second (Kbps)
- Bus Topology: Linear bus with parallel connection of all modules
- Voltage Specifications: CCD+ ≈ 2.5V, CCD- ≈ 2.5V (summing to approximately 5V differential)
- Termination: Two 120-ohm resistors in parallel (60-ohm equivalent) at network ends
2.0 Symptoms & Vehicle Behavior Analysis
When P1694 is stored in the PCM’s memory, the vehicle will exhibit one or more of the following operational symptoms, depending on the severity of the communication failure:
| Symptom Severity | Specific Symptoms | Vehicle Operational State | Immediate Action Required |
|---|---|---|---|
| Severe | Engine no-start condition, Cranks but won’t start | Vehicle inoperable | YES – Tow to shop |
| High | Engine starts but stalls immediately, Intermittent stalling while driving | Unsafe to drive | YES – Immediate repair |
| Moderate | Check Engine Light illuminated, Loss of instrument cluster functions, No RPM or speedometer reading | Limited operation possible | Within 24 hours |
| Low | Other CCD bus codes present, Intermittent communication with scan tool, Delayed engine start | Operational with reduced functionality | Within 1 week |
2.1 Secondary Symptom Manifestations
Additional symptoms may include:
- Multiple Module Communication Loss: Simultaneous DTCs from TCM, BCM, or ABS modules
- Scan Tool Communication Issues: Inability to connect to ECM or intermittent connection drops
- Security System Activation: Vehicle Anti-Theft System (VATS) may prevent starting
- Transmission Limp Mode: Automatic transmissions may default to 2nd gear only
- Erratic Electrical Behavior: Random accessory activation, gauge sweeping, or warning light illumination
3.0 Root Cause Analysis & Component Failure Modes
P1694 can be caused by failures in several areas of the vehicle’s electrical and communication systems. The following table categorizes potential causes by probability and diagnostic complexity:
| Probability | Component/System | Specific Failure Mode | Diagnostic Complexity | Repair Cost Estimate |
|---|---|---|---|---|
| 35% | CCD Bus Wiring/Connectors | Open circuit in CCD+ or CCD- wires, Corrosion at connectors C1/C2, Wire chafing against chassis | Medium | $150-$400 |
| 25% | ECM Power/Ground Circuits | Blown ASD relay fuse, Corroded ground G102/G103, Loose battery connections | Low-Medium | $100-$300 |
| 20% | Engine Control Module (ECM) | Internal processor failure, Power supply circuit failure, Memory corruption | High | $600-$1200 |
| 15% | Other Network Modules | TCM shorting bus to ground, BCM internal failure, Instrument cluster failure | High | $300-$800 |
| 5% | PCM Gateway Failure | PCM internal network controller failure, Software corruption | Very High | $800-$1500 |
3.1 Detailed Wiring Fault Analysis
The CCD bus wiring is particularly susceptible to specific failure modes:
| Wire Color (Typical) | Circuit Designation | Normal Voltage (Key ON) | Failure Symptoms | Test Procedure |
|---|---|---|---|---|
| Dark Blue/Yellow | CCD+ (Positive Data) | 2.4V – 2.6V | Static 0V = Short to ground, Static 12V = Short to power | Measure to chassis ground |
| Dark Blue/White | CCD- (Negative Data) | 2.4V – 2.6V | Identical voltage to CCD+ = Short together | Measure differential to CCD+ |
| Pink/Black | ECM Power (Fused) | 12.0V – 14.5V | Voltage < 11V = High resistance | Voltage drop test |
| Black/White | ECM Ground G102 | 0V – 0.1V | Voltage > 0.5V = Poor ground | Voltage drop to battery negative |
4.0 Professional Diagnostic Procedure
4.1 Preliminary Checks
Measure battery voltage (should be 12.4V minimum). Check all fuses related to ECM and PCM power circuits, particularly fuse #11 (10A) in the PDC for ASD relay control.
Connect a professional-grade scan tool capable of Chrysler-specific diagnostics. Check for additional CCD bus codes (P1695, P1696, P1698) and note all modules that are not communicating.
Inspect ECM connectors C1 (Black) and C2 (Gray) for corrosion, bent pins, or moisture. Check wiring harness for chafing, especially where it passes through the firewall or near sharp edges.
4.2 Electrical Testing Procedure
With key ON, test for battery voltage at ECM connector C2 pin 2 (Pink/Black wire). Perform voltage drop test from battery positive to ECM pin (should be < 0.5V).
Test ground circuit resistance from ECM connector C1 pin 16 (Black/White) to battery negative terminal (should be < 0.5 ohms). Perform voltage drop test with key ON and minimal load (should be < 0.1V).
Measure voltage between CCD+ and ground (should be 2.5V ± 0.1V). Measure voltage between CCD- and ground (should be 2.5V ± 0.1V). Measure differential voltage between CCD+ and CCD- (should be approximately 0V with data activity).
Disconnect battery and measure resistance between CCD+ and CCD- at the ECM connector (should be 60-70 ohms indicating proper termination). Resistance of 120 ohms suggests one termination resistor open. Infinite resistance indicates open circuit in bus.
4.3 Module Isolation Procedure
With battery disconnected, systematically disconnect each module on the CCD bus one at a time, reconnecting battery and checking if communication returns to the ECM. Common modules: TCM, BCM, Instrument Cluster, ABS, and AC Control Module.
Using a DVOM set to ohms, test for continuity between CCD+ and ground, and CCD- and ground (should be infinite resistance). Test between CCD+ and 12V power (should be infinite resistance).
5.0 Component-Specific Repair Protocols
| Fault Identified | Required Parts | Special Tools | Labor Time | Programming Required |
|---|---|---|---|---|
| CCD Wiring Repair | 18 AWG stranded wire, Heat shrink tubing, Weatherpack connectors | Crimping tool, Soldering iron, Heat gun | 1.5-3.0 hours | NO |
| ECM Replacement | New/remanufactured ECM, ECM mounting bolts | DRB-III or equivalent scanner, Security code retrieval tool | 2.0-3.0 hours | YES – VIN programming, security pairing |
| Ground Circuit Repair | Ground strap, Ring terminals, Dielectric grease | Wire brush, Socket set, Torque wrench | 0.5-1.5 hours | NO |
| Connector Repair | Terminal repair kit, Contact cleaner, Dielectric grease | Terminal removal tools, Magnifying glass | 1.0-2.0 hours | NO |
6.0 Frequently Asked Questions
Not recommended. P1694 indicates loss of communication with the engine computer. This can lead to sudden engine stalling, inability to restart, or erratic vehicle behavior. In most cases, the vehicle will either not start or enter limp mode with severely reduced functionality. If the vehicle does start and run, limit driving to emergency situations only and proceed directly to a repair facility.
Repair costs vary significantly based on root cause:
- Wiring repair: $200-$500 (diagnosis and repair)
- ECM replacement: $800-$1500 (including programming)
- Diagnostic fee: $100-$200 (professional diagnosis)
- Dealer repair: Typically 20-40% higher than independent shops
Always obtain a proper diagnosis before approving ECM replacement.
Yes, absolutely. Weak batteries (below 12.2V) or poor battery connections are common causes of network communication issues. Low system voltage can cause modules to reset or fail to communicate properly. Always perform a load test on the battery and check all connections at the battery, starter, and ground points before beginning complex diagnostics.
Basic diagnosis requires:
- Digital Multimeter (DVOM) with min/max recording
- Quality scan tool with Chrysler-specific software
- Wiring diagrams for your specific vehicle
- Terminal probe kit for back-pinning connectors
For ECM replacement, you will need a DRB-III compatible scanner or equivalent with security access capabilities for VIN programming and SKIM pairing.
ECM replacement is confirmed when:
- All power and ground circuits test perfect (< 0.5V drop)
- CCD bus voltages and resistances are correct at ECM pins
- No other modules are shorting the bus (isolation test passed)
- ECM connector pins are clean and properly seated
- ECM shows no signs of physical damage or water intrusion
If all these conditions are met and the ECM still doesn’t communicate, internal failure is confirmed. Some ECMs can be repaired by specialized electronics shops for 50-70% of replacement cost.
