U0073 on 2018-2024 Jeep Wrangler: Control Module Communication Bus 'A' Off Causes and Fixes

What's Unique About the 2018-2024 Jeep Wrangler

While U0073 is a generic network code, the Wrangler JL's electronics have specific weak points. The dual-battery system, with its failure-prone auxiliary battery, is a primary source of low-voltage conditions that trigger communication faults. Furthermore, the CAN bus wiring is routed through junction blocks called 'Star Connectors,' which are known failure points located behind the glove box; wiggling these wires can often temporarily resolve symptoms, pointing to a bad connector. For the 2018 model year specifically, FCA issued a safety recall (18V632000) for a faulty Powertrain Control Module (PCM) that could cause stalling, a key symptom of this code.

Symptoms You May Notice

• Multiple warning lights on the dashboard (Check Engine, ABS, Traction Control, etc.)
• Engine may stall, fail to start, or crank but not turn over
• Vehicle enters 'limp mode' with reduced power
• Erratic or non-functional gauges on the instrument cluster, speedometer may show dashes
• Transmission may shift harshly or not at all
• Loss of electronic features like power windows, radio, or auxiliary switches
• Loss of power steering assist at low speeds

Most Likely Causes

1. Failing Auxiliary Battery / Dual-Battery System 🔴 High Probability The JL/JT platform's dual-battery system for the Engine Start-Stop (ESS) feature is a notorious weak point. The smaller auxiliary battery often fails, causing unstable voltage across the entire electrical system, which is a primary trigger for communication codes like U0073.
   How to confirm: Symptoms often include an 'ESS Unavailable' message. A load test is required on BOTH the main and auxiliary batteries. A simple voltage check is insufficient. A failing aux battery can drain a healthy main battery.
   Typical fix: Replace the auxiliary battery, and often the main battery 🎬 Watch: A simple walkthrough for replacing your auxiliary battery. at the same time. Some owners choose to bypass the auxiliary battery completely.
   Est. part cost: $100-$200 for auxiliary battery
2. Faulty CAN Bus Star Connector 🟡 Medium Probability The CAN bus network on the JL relies on star-shaped junction connectors. The primary one is located behind the glove box and is a known point of failure, causing intermittent network-wide communication loss. The solder joints on the internal circuit board are known to crack, causing intermittent open circuits.
   How to confirm: With the vehicle acting up (dash lights on, etc.), open the glove box and wiggle the bundle of wires going into the star connector. 🎬 See how a faulty star connector causes these dashboard errors. If the symptoms clear up or change, the connector is faulty. Visual inspection of the connector's internal circuit board may reveal cracked solder pins.
   Typical fix: Replace the star connector block. It is a plug-and-play component. 🎬 Watch: How to remove and replace the green star connector.
   Est. part cost: $40-$60
3. Damaged Wiring or Corroded Connectors 🟡 Medium Probability The Wrangler's exposure to off-roading (water, mud, vibration) and aftermarket modifications can lead to damaged wiring harnesses, loose connectors, or corrosion in the CAN bus circuits.
   How to confirm: Visually inspect major wiring harnesses for chafing, cuts, or corrosion, especially where they pass through the firewall, under the vehicle, and near the battery. Check major ground straps for tightness and corrosion.
   Typical fix: Repair the damaged section of the harness or clean/replace the affected connector. This is often a labor-intensive process.
   Est. part cost: $20-$500
4. Faulty Powertrain Control Module (PCM) ⚪ Low Probability A specific recall was issued for some 2018-2019 Jeep Wranglers and other FCA vehicles for faulty PCMs that could cause communication loss and stalling.
   How to confirm: Check your vehicle's VIN for open recalls on the NHTSA or Mopar website. A professional diagnosis is needed to confirm a module failure, typically by trying to communicate with it directly and then isolating it from the network.
   Typical fix: Replace and reprogram the Powertrain Control Module. This must be done by a dealer or a qualified shop with programming capabilities.
   Est. part cost: $500-$1500

Rare But Worth Checking

• Faulty ABS or Body Control Module (BCM): While the PCM is a suspect, any major module on the CAN bus can fail and bring down the network. If other codes point to a specific system (like ABS or BCM), that module becomes a primary suspect.
• Interference from Aftermarket Devices: Wranglers are heavily modified. Improperly installed aftermarket stereos, alarms, remote starters, or lighting can tap into the wrong wires and introduce electrical noise onto the CAN bus, causing communication errors.

Diagnosis Steps

1. Check for open recalls (especially PCM recall 18V632000) and TSBs for your vehicle's VIN.
2. Perform a full load test on BOTH the main and auxiliary batteries. Voltage alone is not a sufficient test. A failing auxiliary battery is the most common cause of electrical issues on this platform.
3. Scan for all codes in all modules. Note which modules are not communicating. The modules that are still online can help pinpoint the location of the break.
4. Check the Star Connector. Open the glove box, locate the connector block, and wiggle the wiring harness while the vehicle is experiencing symptoms. If the dash lights flicker or normalize, the star connector is likely faulty and needs replacement.
5. Visually inspect all major ground connections, battery terminals, and power distribution points for looseness or corrosion.
6. Inspect the main CAN bus wiring harness for any visible damage, chafing, or corrosion, paying close attention to areas exposed to the elements or near aftermarket modifications.
7. Using a multimeter, check for 60 ohms of resistance across the CAN High and CAN Low pins at the OBD-II port (with the battery disconnected). A reading of 120 ohms suggests a break in the circuit or a missing terminating resistor; a reading near 0 ohms suggests a short.
8. If a specific module is suspected, disconnect it from the network and see if communication between other modules is restored. This indicates the disconnected module was likely causing the failure.
9. If the above steps do not isolate the issue, professional diagnosis with an oscilloscope may be needed to analyze the data signals on the CAN bus directly.

Parts You'll Likely Need

• Auxiliary Battery (OEM #68647042AA, 56029759AB) — The most frequent cause of communication codes on the JL/JT platform due to voltage instability when it fails.
  Trusted brands: Mopar, Deka, Interstate (AUX14)
  OEM price range: $150-$200
  Aftermarket price range: $100-$150
• CAN Bus Star Connector (OEM #68321746AA (20-way), 68230877AA (13-way)) — A known failure point located behind the glove box that causes intermittent, network-wide communication loss.
  Trusted brands: Mopar
  OEM price range: $40-$60
• Powertrain Control Module (PCM) — A known failure point, especially on 2018-2019 models subject to a recall. A faulty PCM can take down the entire communication network.
  Trusted brands: Mopar
  OEM price range: $800-$1500

Related Codes That Often Appear With This One

• U0100 — Lost Communication with ECM/PCM. This is often seen with U0073 as it specifies which module is not communicating.
• U0101 — Lost Communication with TCM. This indicates the transmission module is offline, a common symptom of the main bus failure.
• U0121 — Lost Communication with ABS Control Module. This indicates the ABS module is offline, another key module on the main CAN bus.
• U0002 — CAN C Bus Off Performance. This is a more severe code indicating the entire network is down, often appearing with U0073 when a major short or faulty module is present.

Technical Service Bulletins (TSBs) & Recalls

• NHTSA Campaign ID: 18V632000 (FCA Recall U87) - Relates to the faulty PCM on 2018-2019 models, a potential cause of network failure.
• TSB 08-087-19 REV. A - Involves flashing the Body Control Module (BCM) to address certain communication DTCs, though not U0073 specifically, it shows a history of software fixes for network issues.
• TSB 23-033-25 - Lists U0121-00 as one of several potential 'Lost Communication' codes, suggesting a broader network failure is possible and pointing to known wiring issues.

Platform-Specific Known Issues

• Safety Recall U87 (NHTSA 18V632000): A faulty Powertrain Control Module (PCM) on some 2018-2019 models could fail, leading to engine stall or a no-start condition, which can manifest as a U0073 code.

Mechanic-Grade Diagnostic Values

• CAN Bus Resistance — expected: ~60 Ω across CAN_H and CAN_L pins (e.g., pins 6 and 14 at OBD-II port) with battery disconnected.. Failure: A reading of ~120 Ω indicates an open circuit or a missing terminating resistor. A reading near 0 Ω indicates a short between the CAN lines. Some owners have reported readings as low as 40 Ω with aftermarket devices installed.
• CAN Bus Voltage (Key On, Engine Off) — expected: Recessive (idle) state: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V. Dominant (active) state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V.. Failure: Voltages that are stuck high, low, or do not switch between states indicate a short, open, or module failure. An oscilloscope is best for viewing this activity.
• System Voltage — expected: At least 12.4V with the engine off; 13.8V to 14.5V with the engine running.. Failure: Low static voltage or unstable running voltage can cause modules to drop off the network, triggering U0073.

Hidden / Shadow Codes Worth Checking

• U1110, U1120, U11BC, etc.: These are secondary 'lost communication' codes that often accompany U0073. For example, U1110 (Lost Wheel Speed Message) or U1120 (Lost Wheel Distance Message) may point towards an issue originating from the ABS system. Advanced scanners like J-scan can read these module-specific codes. (see via Advanced consumer scan tools (like J-scan, BlueDriver) or professional/dealer tools (wiTECH).)

Scan Tool Commands That Help

• wiTECH 2 (Dealer Tool): PCM Programming / VIN Writing — Required when installing a new or blank PCM. The tool flashes the correct software and writes the vehicle's VIN to the new module to sync it with the immobilizer and other systems.
• wiTECH 2 (Dealer Tool): Throttle Pedal Learn Procedure — This is a routine that may be required after replacing and programming a PCM to calibrate the electronic throttle body.
• Advanced Scan Tool (Autel, J-scan, etc.): Network Topology / Module Status — To get a visual map of all control modules on the network and see which ones are online (communicating) and which are offline (not responding). This is a critical step to isolate the location of the network failure.

Wiring & Ground Locations

• CAN Bus Star Connectors — Behind the glove box. There is a green 20-way connector (PN 68321746AA) and often a white 13-way connector (PN 68230877AA).. This is the central hub for the CAN C bus. Internal cracked solder joints are a very common failure point on the JL, causing a total network shutdown.
• Security Gateway Module (SGW) — Located behind and slightly above the OBD-II port, under the driver's side dashboard.. This module controls access to the diagnostic network. While not a common failure, its location is critical for installing a bypass jumper, which is needed for some aftermarket tuning and advanced diagnostics.
• Head Unit Connector Pins — On the main 52-pin connector for the base radio, CAN C (+) is Pin 1 (Gray wire) and CAN C (-) is Pin 11 (Yellow/Violet wire) for a 2019 model.. If U0073 appears after a stereo installation, these are the specific pins to check for damage or improper connection from an aftermarket wiring adapter (like a Maestro).
• CAN C Body / IP Star Connectors — Wiring diagrams refer to the connectors behind the glove box as 'CONNECTOR - STAR CAN C BODY' and 'CONNECTOR - STAR CAN C IP' (Instrument Panel).. These are the official technical names for the star connectors, useful when referencing service manuals or wiring diagrams.

Real Owner Repair Stories

• YouTube user, video title 'Jeep wrangler CAN-C canbus error FIX' (2019 Jeep Wrangler JLU) — Dashboard lit up with every possible error, engine would die, loss of power steering, wipers turning on by themselves, service transmission warning.
  ❌ Tried (didn't work) Vehicle was at the dealership for two months without a resolution.
  ✅ What actually fixed it The owner replaced the green CAN bus star connector (Mopar PN 68321746AA) located behind the glove box. This resolved all symptoms.
• Reddit user on r/Jeep (Jeep Wrangler JL/JT (specific year not mentioned)) — Dashboard lit up 'like a Christmas tree,' loss of power steering and speedometer on the highway.
  ❌ Tried (didn't work) Initially considered replacing the entire star connector block.
  ✅ What actually fixed it The owner removed the green star connector block behind the glovebox, opened it, and found cracked solder joints on nearly every pin. Re-soldering the pins on the connector's internal circuit board fixed the problem.
• YouTube user, video title 'Jeep Wrangler Star Connector Failure' (Jeep Wrangler (JL implied, fits 2017+ Mopar vehicles)) — Service Shifter warning, Service Electronic Stability Control, multiple DTCs, won't shift out of park, vehicle goes into limp mode, no-start.
  ✅ What actually fixed it Replaced the CAN bus star connector (PN 68321746AA). The video shows the back of the connector's circuit board, revealing that the solder around the pins had separated, causing the intermittent connection.

"I Checked Everything" — The Actual Cause

• This is an electrical fault where a smoke test is not applicable. However, a common pattern is that initial voltage and resistance checks on the CAN bus may appear normal if the fault is intermittent. The true cause is often a mechanical failure inside the star connector block (cracked solder joints) that isn't visible externally. The 'wiggle test' on the star connector harness is the non-standard diagnostic step that often reveals this hidden failure when standard electrical tests do not.

OEM Part Supersession History

• 68321746AA → No supersession found in research. — This part number appears to be current and fits a wide range of FCA vehicles from 2017 through 2022+.

Model Year Variations Within This Range

• 2024+: The 2024 model year refresh introduced a completely new dashboard design with a standard 12.3-inch screen and rectangular center vents. This makes dash-mounted accessories (phone holders, storage trays) for 2018-2023 models incompatible. The antenna was also moved from the fender to the windshield. These physical and electrical changes can alter wiring routes and diagnostic approaches for issues caused by aftermarket accessories.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Frame Weld Quality Issues 🔴 High — Most prominent on 2018-2019 models. A recall was issued, but complaints of poor welds persist across the generation. (Ref: NHTSA Recall 18V-675 addressed front track bar bracket welds, but broader weld quality concerns have been investigated.)
• Steering Shimmy / "Death Wobble" 🟠 Medium — Common across 2018-2020 models, especially after hitting bumps at highway speeds. (Ref: Customer Satisfaction Notification V41 was issued to replace the front suspension steering damper.)
• Auxiliary Battery Failure (ESS Battery) 🔴 High — Extremely common across all JL/JT models, often failing within 2-4 years. It causes a cascade of electrical issues and no-start conditions.
• Galvanic Corrosion on Body Panels 🟠 Medium — Affects aluminum panels like doors and hinges, causing paint bubbling. Widely reported on 2018-2022 models. (Ref: TSB 31-001-23 addresses the corrosion repair procedure; warranty was extended from 3 to 5 years for this issue.)
• Clutch Pressure Plate Overheating (Manual Transmission) 🔴 High — Affects 2018-2023 models with manual transmissions, potentially leading to fire. (Ref: NHTSA Recalls 20V124000, 21V239000, 23V116000)

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For the CAN Bus Star Connector, a used part from a reputable auto recycler is a reasonable choice. It is a simple, non-wear item, and a visual inspection is usually sufficient to determine its condition.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• Ensure the plastic housing is not cracked or brittle.
• Inspect the pins to ensure none are bent, corroded, or pushed in.
• If possible, check for signs that the connector has been previously opened or tampered with.

OEM-only on this vehicle (don't cheap out):

• Powertrain Control Module (PCM): While used PCMs can be purchased, they are not plug-and-play. They MUST be professionally reprogrammed (flashed) with the vehicle's VIN and security information using dealer-level tools like wiTECH to function. An incorrectly programmed PCM will result in a no-start condition.

Aftermarket brands forum-validated for this vehicle:

• Diagnostic Tools: OBDLink (MX+), J-scan (App)
• Stereo Integration: iDatalink (Maestro)

Brands owners have reported issues with on this vehicle:

• No specific brands were consistently reported as problematic for replacement parts, but extreme caution is advised with no-name electronic components that interface with the CAN bus.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• U0121-00 — A 'Lost Communication' code cited in TSB 23-033-25 that can appear alongside U0073 during broader network or wiring failures.
• U0100 — Often accompanies U0073 when the Powertrain Control Module (PCM) fails or loses communication due to voltage instability from the dual-battery system.
• U0140 — Related to the Body Control Module (BCM); software flashes for this module are noted in TSB 08-087-19 to resolve communication DTCs.
• B1234 — Generic representation of various communication-related DTCs that can trigger when the CAN bus star connector solder joints crack.

Frequently Asked Questions