🚨 Diagnostic Profile
Vehicle Make: Dodge
Description: Speed control power relay or speed control 12 volt driver circuit open or shorted. The speed control system has detected a fault in the power supply or driver circuit that feeds the speed control servo.
🚨 Repair Difficulty Tier
Tier: [Intermediate]
Relay replacement is a basic task, but tracing an open or shorted 12 volt driver circuit requires a digital multimeter, access to the wiring diagram for the specific model year, and basic circuit diagnosis skills.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
- Verify battery voltage is at a healthy resting state (typically 12.4V-12.6V key off) and confirm charging system output climbs to the normal charging range (typically 13.5V-14.7V) with the engine running, using a digital multimeter at the battery posts.
- Visually inspect the speed control power relay, typically located in the under-hood power distribution center (PDC) or integrated power module (IPM), for corrosion, burnt terminals, heat discoloration, or loose/spread connector pins.
- Inspect the speed control servo harness and connector, typically located near the throttle body or firewall on cable-actuated systems, for chafing, pinched wires, moisture intrusion, or corroded/spread pin terminals.
- Check the brake switch and clutch switch (if equipped) for proper mechanical operation, correct adjustment/travel, and confirm they open and close circuits as designed when the pedal is actuated.
- Confirm that the fuse or circuit breaker protecting the speed control circuit, typically located in the interior fuse block or underhood PDC per the label on the fuse box cover, is intact and rated to the amperage specified on the fuse box legend for that vehicle’s model year.
Step 2: Diagnostic Verification
- Retrieve and record all stored and pending diagnostic trouble codes with an OBD-II capable scan tool before clearing anything, noting freeze frame data if available.
- With the ignition off, disconnect the relay and test coil resistance across the relay’s control circuit terminals using an ohmmeter, comparing the reading against the relay manufacturer’s specification (typically in the 70-120 ohm range for standard automotive relays, but verify against the specific relay part number stamped on its housing).
- With the ignition on, verify battery voltage is present at the relay’s constant power supply terminal and confirm switched voltage appears at the relay output terminal when commanded, using a digital multimeter referenced to a verified clean chassis ground.
- With the ignition off and the harness disconnected at both ends, check the driver circuit wire for continuity end-to-end and test for shorts to ground or to voltage, cross-referencing the factory wiring diagram circuit identifier for the specific model year to correctly locate the driver circuit wire among the harness.
- Command the speed control servo through the scan tool’s bidirectional controls or actuator test menu, if supported by the platform, and confirm the driver output responds with movement or a measurable voltage/duty-cycle change at the servo connector.
Step 3: Resolution & Reset Process
- Replace the speed control power relay if it fails coil resistance, output voltage, or switching tests, ensuring the replacement relay matches the OEM part number or verified cross-reference exactly.
- Repair any open, chafed, or shorted section of the driver circuit using the correct gauge wire (matching factory gauge, typically 18-20 AWG for control circuits) with proper weatherproof heat-shrink butt connectors or solder-and-seal splices, then secure the repair with loom and anchor points away from heat sources and moving parts.
- Replace the speed control servo only if internal testing confirms an internal fault after the power supply and driver circuit have both been verified good and within specification.
- Clear all diagnostic trouble codes using the scan tool and perform a complete key cycle (key off for at least 10 seconds, then key on).
- Road test the vehicle to confirm that the speed control engages, holds set speed within normal tolerance, and cancels correctly from both the steering wheel switches and the brake pedal (and clutch pedal if manual transmission equipped).
- Recheck for stored or pending codes after the road test using the scan tool to confirm the repair is complete and no new faults have surfaced.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: OEM or OEM-equivalent speed control power relay ($15-$45 depending on model year and relay design), automotive wire repair kit with weatherproof butt connectors and heat-shrink tubing ($10-$25), speed control servo assembly if confirmed faulty ($150-$400 for the unit alone), OBD-II scan tool capable of bidirectional control and live data streaming (shop-grade tools range $300-$3,000; dealer-level software such as Chrysler’s wiTECH subscription runs approximately $45-$70 for a short-term access window if outsourced to a dealer).
Average Component Price: $15-$45 for relay only; $150-$400 if servo replacement is required; wiring repair materials typically under $25.
Estimated Labor Hours: 0.5-1.0 hour for diagnostic inspection and relay replacement; 1.0-2.0 hours for wiring circuit tracing and repair depending on harness accessibility; 0.8-1.2 hours for speed control servo replacement (labor rates vary by shop, typically $100-$170 per hour).