Technical Definition & System Overview
Diagnostic Trouble Code P1392 is defined as “Auto Shutdown (ASD) Relay Control Circuit” and is specific to Chrysler Corporation vehicles (Chrysler, Dodge, Jeep, Ram). This code indicates an electrical fault in the circuit that controls the Auto Shutdown relay—a critical component that manages power distribution to essential engine systems.
The ASD system is a safety-critical component designed to cut power to the fuel pump, fuel injectors, and ignition coils when the ignition is turned off or when the engine is not running. This prevents fuel delivery and ignition spark when not needed, reducing fire risk and unintended operation.
Professional Insight: The ASD relay is controlled by the Powertrain Control Module (PCM) through a ground-side switching circuit. When the PCM detects the engine is running (via crankshaft position sensor), it grounds the ASD relay control circuit, energizing the relay and providing power to critical engine components.
Affected Vehicle Systems
- Fuel Delivery System – Fuel pump, injectors, pressure regulator
- Ignition System – Ignition coils, spark plugs, ignition module
- Engine Control Module (PCM) – Primary vehicle computer
- Power Distribution System – Fuses, relays, wiring harness
- Vehicle Safety Systems – Anti-theft, crash detection
Safety Warning: Driving with an active P1392 code can result in sudden, unexpected engine shutdown while driving—especially at highway speeds. This creates immediate crash risks. Immediate diagnosis and repair are strongly recommended.
Comprehensive Symptoms & Diagnostic Indicators
Primary & Immediate Symptoms
- Complete no-start condition – Engine cranks normally but fails to start (most common)
- Intermittent stalling – Engine suddenly shuts off while driving, especially under load
- Extended cranking time – Engine requires prolonged cranking before starting
- Start-then-die syndrome – Engine starts but immediately stalls within seconds
- Illuminated Check Engine Light (often with multiple related codes)
Diagnostic Tip: When experiencing a no-start with P1392, listen for the fuel pump priming when turning the key to RUN position. No fuel pump sound often confirms ASD relay failure.
Performance & Drivability Issues
- Severe engine misfires, especially under acceleration
- Rough idle with fluctuating RPM (200-300 RPM variation)
- Hesitation, stumbling, or bucking during acceleration
- Reduced engine power and poor throttle response
- Decreased fuel economy (15-30% reduction)
- Intermittent loss of electrical accessories
Note: Performance symptoms often worsen with engine temperature increases or electrical load (AC, headlights, etc.).
Electrical & Secondary Symptoms
- Intermittent or complete loss of power to fuel injectors
- No voltage at ignition coils when cranking or running
- Audible relay clicking without power output
- Parasitic battery drain (vehicle battery dies overnight)
- Other electrical anomalies (flickering lights, gauge issues)
- Multiple seemingly unrelated trouble codes appearing
Battery Warning: Continuous cranking with a faulty ASD relay can drain battery quickly. Use a battery charger during diagnosis to prevent additional issues.
Root Causes & Failure Analysis
Electrical & Component Failures
Most Common (65-75% of cases)
- Failed ASD relay – Internal contacts worn, coil failure, thermal damage
- Blown fuse – ASD fuse (typically 20A-40A) blown due to short or overload
- Damaged wiring – Chafed, pinched, or rodent-damaged wires in control circuit
- Corroded connectors – Water intrusion causing terminal corrosion
- Faulty relay socket – Burnt, melted, or loose terminals in PDC
Less Common (15-25% of cases)
- Short to ground or power in control circuit
- Open circuit between PCM and relay
- High resistance in control circuit (>5 ohms)
- Damaged Power Distribution Center (PDC)
PCM & Control System Issues
PCM-Related Causes (5-10% of cases)
- Faulty PCM driver circuit – Internal failure of relay control circuit
- PCM ground issues – Poor PCM grounding affecting output signals
- PCM power supply issues – Unstable voltage to PCM affecting outputs
- Intermittent PCM communication – Network issues affecting relay control
Complex/Systemic Issues (5-10% of cases)
- Multiple electrical faults affecting entire system
- Previous repair damage (incorrect wiring, wrong relay)
- Vehicle-specific Technical Service Bulletin (TSB) issues
- Aftermarket alarm/security system interference
Diagnostic Priority: Always start with simplest causes (relay, fuse) before progressing to complex PCM diagnosis. 85% of P1392 cases are resolved with relay/fuse/wiring repairs.
Vehicle-Specific Common Issues
By Vehicle Model
- Jeep Grand Cherokee (WJ/WK) – PDC moisture intrusion, relay socket corrosion
- Dodge Ram (3rd/4th Gen) – Wiring harness chafing near PCM
- Chrysler 300/Dodge Charger – Aftermarket accessory wiring interference
- Jeep Wrangler (TJ/JK) – Water exposure issues, off-road damage
- Dodge Caravan/Chrysler Town & Country – Rodent damage to underhood wiring
By Engine Type
- 3.3L/3.8L V6 – Common in minivans, typically relay failure
- 4.0L I6 – Jeep applications, often wiring/connector issues
- 5.7L HEMI V8 – Higher electrical loads, relay contact failure
- 2.4L I4 – Less common, usually simple relay replacement
Advanced Diagnostic Procedures & Protocols
Initial Diagnostic Scan & Code Verification
Begin with a professional-grade OBD2 scanner capable of reading manufacturer-specific codes and live data. Confirm P1392 is present and active (not pending or historic). Record all freeze frame data including RPM, engine load, temperature, and vehicle speed when code set. Check for related codes (P1390, P1391, P1388, P1682, fuel/ignition codes).
Pro Tip: Use bidirectional scanner controls to command ASD relay ON/OFF if supported. This tests both PCM control capability and relay function directly.
Visual Inspection & Basic Electrical Checks
Locate ASD relay (typically in underhood Power Distribution Center). Inspect thoroughly:
- Check for physical damage, melted plastic, or burning smell
- Inspect relay socket for corrosion, bent pins, or burnt terminals
- Check related fuses (ASD fuse, PCM fuse, ignition fuse)
- Inspect wiring harness for chafing, especially near PCM and PDC
- Check for aftermarket accessories tapping into ASD circuit
- Verify battery condition and charging system operation
Important: Never force a relay into its socket. Bent pins can cause short circuits and PCM damage. If pins are bent, repair socket before proceeding.
ASD Relay Testing & Circuit Analysis
Using a digital multimeter, perform comprehensive relay testing:
ASD Relay Circuit Analysis Points
85: PCM Control | 86: Ground
87: Load Output | 30: Battery Power
Testing Procedure:
- Bench test relay – Apply 12V to coil terminals (85/86), check for click and continuity between 87/30
- Power circuit test – Check for constant 12V at terminal 30 with key OFF
- Control circuit test – Check for PCM-provided ground at terminal 85 with key ON/engine cranking
- Output test – Verify 12V at terminal 87 when relay energized
- Swap test – Exchange ASD relay with identical relay (horn, AC, etc.)
Wiring & PCM Circuit Diagnosis
If relay tests good, diagnose control circuit between PCM and relay:
| Test | Procedure | Expected Result | Failure Indication |
|---|---|---|---|
| Continuity Test | Test wire from relay pin 85 to PCM connector | Less than 1 ohm resistance | Open circuit >5 ohms |
| Short to Ground Test | Test relay pin 85 to chassis ground | No continuity (OL on meter) | Short to ground |
| Short to Power Test | Test relay pin 85 to battery positive | No continuity (OL on meter) | Short to power |
| Voltage Drop Test | Test voltage across circuit under load | Less than 0.5V drop | High resistance in circuit |
PCM Testing: If wiring tests good, suspect PCM issue. Check PCM power and ground circuits before condemning PCM. Use oscilloscope to monitor control signal from PCM during cranking.
Advanced & Intermittent Fault Diagnosis
For elusive intermittent faults, employ advanced techniques:
- Wiggle testing – Manipulate wiring harness while monitoring circuit
- Thermal testing – Use heat gun/cool spray to induce temperature-related faults
- Voltage waveform analysis – Use oscilloscope to examine PCM control signal quality
- Current ramping – Analyze relay coil current draw pattern for abnormalities
- Network diagnosis – Check CAN bus communication affecting PCM operation
Diagnostic Logic: Always diagnose from simplest to most complex. 85% of P1392 cases are resolved at steps 1-3. Only proceed to advanced diagnostics if basic tests pass but symptoms persist.
Comprehensive Repair Cost Analysis
| Repair Scenario | Parts Cost Range | Labor Time | Total Estimate | Complexity | Warranty |
|---|---|---|---|---|---|
| ASD Relay Replacement Only (65% of cases) | $25 – $80 (OEM vs aftermarket) |
0.3 – 0.5 hours | $75 – $180 | Low | 1-2 years |
| ASD Relay + Fuse Replacement | $30 – $90 | 0.4 – 0.6 hours | $85 – $200 | Low | 1-2 years |
| Wiring Repair (Basic) Single wire repair, connector |
$40 – $120 | 1 – 2 hours | $150 – $350 | Medium | Varies |
| Wiring Harness Section Replacement | $150 – $400 | 2 – 4 hours | $350 – $800 | Medium | Varies |
| PCM Repair/Reprogramming | $200 – $500 | 1 – 1.5 hours | $300 – $650 | High | 90 days – 1 year |
| PCM Replacement (New OEM) | $400 – $1,200+ | 1 – 1.5 hours + programming | $500 – $1,400+ | High | 1-3 years |
| Complete Diagnostic Only Professional shop diagnosis |
N/A | 0.5 – 2 hours | $100 – $250 | Low | N/A |
DIY Repair vs Professional Service Comparison
| Consideration | DIY Repair | Professional Service | Recommendation |
|---|---|---|---|
| Cost | $25-$120 (parts only) | $75-$1,400+ (parts + labor) | DIY for simple relay replacement only |
| Tools Required | Basic hand tools, multimeter | Full diagnostic suite, scan tools | Professional for complex diagnosis |
| Technical Skill | Intermediate automotive electrical | Certified technician expertise | Match skill level to repair complexity |
| Time Investment | 1-4 hours (variable) | 0.5-3 hours (predictable) | Professional saves time for complex cases |
| Warranty/Guarantee | None (self-performed) | 1-3 years parts & labor | Professional for expensive repairs |
| Risk Factor | Higher (misdiagnosis, damage risk) | Lower (insured, expertise) | Professional for PCM/wiring repairs |
Expert FAQ & Technical Insights
Not recommended and potentially dangerous. While technically possible to jump power to the fuel pump and ignition systems, this bypasses critical safety features. The ASD system prevents fuel delivery and ignition when the engine isn’t running (crash safety). Bypassing could create fire hazards and may damage PCM or other components. If stranded, consider towing instead.
Recurring P1392 after relay replacement indicates underlying circuit issues. Common causes include:
- Damaged relay socket – Burnt terminals creating high resistance
- Wiring issues – Intermittent opens/shorts in control circuit
- PCM driver circuit failure – PCM unable to properly control relay
- Incorrect relay type – Using wrong specification relay
- Power distribution issues – Problems in PDC or main power feeds
Proper diagnosis should include voltage drop testing, wiring inspection, and PCM circuit analysis.
The ASD system is integrated with vehicle security on many Chrysler vehicles. The PCM will not energize the ASD relay if:
- Invalid key is detected (SKIM system)
- Security system is armed/alarming
- Crash signal is detected (airbag deployment)
- PCM doesn’t receive valid enable signal from BCM
If you have both P1392 and security-related codes (P1683, P1684), diagnose security system first. A faulty SKIM module or key can cause P1392.
| Code | Definition | Circuit | Primary Difference |
|---|---|---|---|
| P1392 | ASD Relay Control Circuit | Control side (PCM to relay) | PCM control circuit fault |
| P1388 | ASD Relay Control | Output side (relay to components) | Relay output circuit fault |
| P1682 | Charging System Voltage High | Charging system | Overvoltage condition |
| P1390/1391 | Timing/CKP Issues | Sensor inputs | Timing/sensor problems |
Key distinction: P1392 specifically indicates a problem in the control circuit between PCM and relay coil. P1388 indicates a problem in the power output circuit from relay to components.
Yes, indirectly. A failing alternator causing voltage irregularities can trigger P1392 through several mechanisms:
- Overvoltage – Charging voltages above 15V can damage relay coil or PCM driver
- Undervoltage – Low system voltage (<9V during cranking) can prevent proper relay operation
- Voltage spikes – Intermittent spikes can disrupt PCM operation
- Ripple voltage – Excessive AC ripple can interfere with electronic components
Always check charging system performance when diagnosing electrical codes. Look for codes P0562/P0563 (system voltage) accompanying P1392.
Professional Recommendation & Best Practices
1. Diagnosis Before Replacement: Never replace the PCM without thorough diagnosis. 85% of P1392 cases are relay, fuse, or wiring issues. PCM failure is relatively rare (<10% of cases).
2. Use OEM Components: For relay replacement, OEM or high-quality aftermarket relays are recommended. Cheap relays often fail prematurely and can damage the control circuit.
3. Address Root Causes: If wiring damage is found, identify and correct the cause (chafing, heat exposure, rodent access) to prevent recurrence.
4. Complete System Testing: After repair, test complete system operation including fuel pump prime, ignition operation, and road test under various conditions.
5. Clear Codes & Verify Fix: Always clear codes after repair and perform multiple drive cycles to ensure the fix is permanent. Monitor for code recurrence for several days.
