How to Fix Diagnostic Code P1320

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🚨 Diagnostic Profile

Vehicle Make: CHRYSLER

Fault Description: IC Module 4X Ref Circuit Intermittent No Pulses

Summary: The instrument cluster (IC) module is reporting an intermittent loss of the 4X reference signal. The fault may be caused by wiring, connector, grounding, or module-side issues, or by a sensor or PCM signal problem upstream of the cluster. Confirm the fault before replacing any components.

🚨 Repair Difficulty Tier

Tier: [Intermediate]

Diagnosis requires circuit testing, signal verification, and connector inspection. Repair may involve harness repair or module replacement, which requires proper programming and reset procedures.

🛠️ Resolution Steps

Step 1: Preliminary Inspection

  • Review stored DTCs and freeze frame data across all modules, noting any related crankshaft, camshaft, or communication faults.
  • Visually inspect the IC module connectors for corrosion, bent or backed-out pins, and loose terminals at the rear of the instrument cluster and at the Powertrain Control Module (PCM) connector, since the 4X reference signal is typically derived from processed crankshaft/engine speed data relayed from the PCM to the cluster.
  • Inspect the wiring harness for chafing, pinching, heat damage, or rodent damage along the routing path between the cluster and the PCM, paying close attention to areas near the firewall grommet and any harness junction connectors.
  • Check battery voltage and charging system output, since low or unstable voltage can cause intermittent signal loss or erratic module behavior.
  • Inspect all ground points associated with the IC module and confirm clean, tight connections at the instrument panel ground distribution point(s) and at the engine block/chassis ground straps feeding the PCM.
  • Check for any recent aftermarket accessory installations, remote start kits, or wiring modifications that could affect the circuit or introduce electrical noise.

Step 2: Diagnostic Verification

  • Connect a scan tool and monitor live data for the 4X reference signal (engine speed/tachometer reference) while wiggling the harness and connectors to try to reproduce the intermittent fault.
  • Verify the expected reference signal at the IC module connector using an oscilloscope: the signal should appear as a clean, consistent digital square-wave pulse train switching cleanly between approximately 0V and the circuit’s reference high level, with pulse frequency correlating directly to actual engine RPM. Dropouts, rounded edges, noise, or erratic pulse spacing indicate a wiring, connector, or source signal problem.
  • Perform a voltage drop test on the supply and ground circuits under load: as a general industry standard, voltage drop should not exceed approximately 0.1V on ground circuits and 0.2–0.3V on powered signal circuits; readings above this indicate corrosion or high-resistance connections.
  • Check continuity and resistance of the signal circuit between the source (PCM) and the IC module with the connectors disconnected and circuit de-energized: resistance should read only a few ohms (typically under 5 ohms) consistent with wire gauge and length; any significantly higher reading indicates a damaged conductor, corroded splice, or poor terminal contact.
  • Check each signal circuit for shorts to ground or shorts to voltage with the circuit unpowered and disconnected: a good circuit should show infinite resistance (open) to chassis ground and no continuity to battery voltage.
  • Confirm the upstream signal source is functioning correctly by monitoring Crankshaft Position Sensor (CKP) and/or Camshaft Position Sensor (CMP) PIDs on the scan tool and, if available, capturing an oscilloscope waveform at the PCM input to confirm the PCM is receiving a clean raw signal and is correctly processing and outputting the 4X reference to the cluster.
  • Review all applicable Technical Service Bulletins (TSBs) and check for open PCM or IC module software/calibration updates through a factory-level scan tool for this specific model and model year.

Step 3: Resolution & Reset Process

  • Repair any identified wiring damage, corroded terminals, or poor grounds using OEM-spec weatherproof crimp-and-seal or solder-and-heat-shrink splice methods matched to the original wire gauge and insulation rating; replace damaged connector housings and terminals with OEM-equivalent parts rather than generic universal splice connectors, to maintain circuit integrity and moisture sealing.
  • Replace the IC module only if testing confirms the module itself is at fault (i.e., a known-good signal is present at the module connector but the cluster fails to register it) and the supply, ground, and signal circuits have all tested within acceptable parameters.
  • If the IC module is replaced, program and configure it using a factory-level diagnostic and programming tool (such as Chrysler’s wiTECH 2.0 with an active subscription), performing VIN synchronization, odometer mileage transfer, module configuration, and any required Sentry Key Immobilizer Module (SKIM) relearn or secure gateway authentication procedure.
  • Clear all DTCs across affected modules and verify no pending or history codes return after a road test that duplicates the original conditions (varying speeds, harness flexing points, and extended drive cycle).
  • Perform a final live data and oscilloscope check to confirm the 4X reference signal remains stable with no dropouts across the full engine RPM operating range, including idle, acceleration, and deceleration.
  • Document all test results, voltage/resistance readings, waveform captures, and parts replaced on the repair order for warranty and future diagnostic reference.

📦 Parts, Labor, and Budget Estimates

Required Components/Software:

  • Diagnostic scan tool with live data and graphing capability (factory-level tool such as wiTECH preferred for Chrysler-specific PIDs)
  • Digital multimeter and back-probe leads
  • Oscilloscope (strongly recommended for accurate signal pulse verification)
  • Replacement connector terminals, weatherproof seals, and wiring as needed — OEM part numbers must be sourced via VIN-specific dealer parts lookup, as terminal and connector part numbers vary by model, year, and cluster/PCM configuration
  • Replacement IC module, if required — OEM part number must be sourced via VIN-specific dealer parts catalog, as clusters are often vehicle-configuration specific
  • Factory service programming software and subscription (Chrysler wiTECH 2.0 or equivalent authorized dealer-level software)

Average Component Price: Wiring/terminal repair kit: $15–$60. Instrument cluster (IC) module replacement: $250–$750 for the part alone depending on model, trim level, and whether it includes additional gauge/telematics features; premium or digital clusters on newer models can exceed $900–$1,200. PCM replacement (only if confirmed as root cause): $400–$900 part cost.

Estimated Labor Hours: Diagnostic time (inspection, circuit testing, and signal verification): 1.0–2.5 hours. Wiring/connector repair: 0.5–1.5 hours. IC module replacement and programming/configuration: 0.7–1.3 hours (shop book time), plus additional 0.3–0.5 hour for SKIM relearn/security sync if applicable. Total estimated labor for full diagnosis-through-repair: 2.0–4.5 hours depending on root cause complexity and whether harness repair or module replacement is required.