🚨 Diagnostic Profile
Vehicle Make: Dodge
Description: High Speed Radiator Fan Control Relay Circuit Open or Shorted. The powertrain control module (PCM) has detected a fault in the high-speed radiator fan relay control circuit. The circuit is either open (no continuity) or shorted to voltage or ground.
🚨 Repair Difficulty Tier
Tier: [Intermediate]
Rationale: Diagnosis requires circuit testing with a digital multimeter and scan tool, and may involve wiring harness and connector repair. The relay itself is a simple replacement, but locating and verifying the fault in the control circuit requires systematic electrical testing.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
- Scan all modules for active and stored DTCs, and record freeze frame data including coolant temperature, fan status, and battery voltage.
- Verify system voltage at the battery: confirm a stable 12.4V-12.6V key-off resting voltage and 13.5V-14.7V with the engine running, as low system voltage can cause false relay control circuit faults.
- Locate the high-speed fan relay: on most Dodge/Chrysler platforms this relay is housed in the underhood Totally Integrated Power Module (TIPM) or Integrated Power Module (IPM) fuse/relay block; consult the label on the underside of the TIPM cover or the vehicle-specific service information for the exact cavity location, as relay box layouts vary by model and year.
- Visually inspect the relay, its socket, and the surrounding connectors for corrosion, melted terminals, backed-out pins, or water intrusion.
- Check the related fuses and the cooling fan power and ground circuits for damage or looseness.
- Confirm cooling fan operation at low and high speed with the engine cold and at operating temperature, if safe to do so.
Step 2: Diagnostic Verification
- Test the relay coil resistance using a digital multimeter and confirm it falls within OEM specification (typical automotive relay coils measure between 50-120 ohms; consult the specific relay’s stamped part number against OEM data for exact spec, as values vary by relay design).
- Verify relay switching by applying battery voltage directly to the coil terminals on the bench and confirming continuity across the output contacts with an ohmmeter; replace the relay if it fails to switch consistently.
- Measure control circuit continuity between the relay socket control pin and the corresponding PCM driver pin using a digital multimeter in resistance mode with the relay removed and the PCM disconnected; continuity should read near 0 ohms with no intermittent dropout when wiggling the harness.
- Check the control circuit for a short to ground with the connector disconnected by measuring resistance from the control circuit to chassis ground; an acceptable reading is open circuit (infinite resistance, OL on the meter).
- Check the control circuit for a short to voltage with the ignition on and the relay removed by probing the control circuit pin with a voltmeter referenced to ground; a reading above 1V with no relay installed indicates an unwanted voltage source.
- Verify the fan motor ground path for resistance and voltage drop under load, confirming less than 0.2V drop across any ground connection while the fan is energized.
- Use a scan tool with bi-directional control capability to command the high-speed fan relay on and off, listening and watching for relay click and fan response, and confirm the PCM output driver activates the circuit as commanded (an oscilloscope may be used to capture the PCM control circuit switching to ground when commanded on).
Step 3: Resolution & Reset Process
- Repair any open, shorted, or corroded wiring, using OEM-approved solder-seal splices or heat-shrink butt connectors and sealed weatherproof connectors where applicable, following factory wire gauge and color-matching practices.
- Replace the high-speed fan relay with an OEM-specification Mopar relay if it failed its coil or contact test, ensuring correct relay amperage rating and pin configuration match the original.
- Replace any damaged fuse or connector terminal, and confirm all connectors are fully seated and locked with an audible click.
- Clear all DTCs with the scan tool and perform the module’s ignition-cycle or drive-cycle relearn if specified in service information.
- Perform a road test or extended idle test to bring the engine to normal operating temperature (coolant temp sufficient to trigger high-speed fan engagement, typically above the thermostat-regulated threshold) and verify high-speed fan activation and correct PCM-commanded cycling.
- Recheck for pending or stored codes and confirm the DTC does not return after completing the OEM-specified drive cycle for the cooling fan circuit monitor.
📦 Parts, Labor, and Budget Estimates
Required Components/Software:
- High-speed radiator fan relay (OEM Mopar relay, typically a 4 or 5-pin ISO-style micro relay)
- Relay socket or connector terminals (if damaged) — OEM Mopar TIPM/IPM pigtail connector repair kit
- Fuse (if required) — mini or maxi fuse matching TIPM fuse box amperage rating specified on the fuse box label
- Wiring repair materials: OEM-grade heat-shrink butt connectors, adhesive-lined loom tape, and automotive-grade GXL wire matched to gauge
- Scan tool with bi-directional controls and current OEM or aftermarket service information subscription (e.g., Snap-on, Autel, or Chrysler witech-level diagnostic access)
Average Component Price:
- Relay: $15 – $45 (OEM Mopar pricing varies by model year and relay design)
- Connector or socket repair kit: $20 – $60
- Wiring repair materials: $10 – $30
- Total parts estimate: $45 – $135
Estimated Labor Hours:
- Diagnosis and circuit testing: 0.8 – 1.5 hours
- Relay or wiring repair: 0.3 – 1.2 hours (relay swap is quick; harness repair adds time depending on accessibility)
- Verification and reset: 0.3 – 0.5 hours
- Total shop book time: 1.4 – 3.2 hours
Additional Notes: If diagnosis points to a failed TIPM/IPM internal driver circuit rather than external wiring or relay failure, replacement of the Totally Integrated Power Module itself may be required, which significantly increases both parts cost ($400 – $900+ for the module alone) and labor (1.5 – 3.0 hours), plus module programming/configuration time using a factory-level scan tool. Always rule out external wiring and relay faults first before condemning the TIPM.