U1108 — SCP (J1850) Invalid or Missing Data for Electric Traction Drive (Inverter) #

Note: The wording of this code may vary depending on the vehicle manufacturer.

• U1108 — J1850 Data Bus: Missing or Invalid Data for Electric Traction Drive (Inverter) (Chrysler)
• U1108 — CAN Communication Error: Inverter Data (Fiat)
• U1108 — Invalid/Missing Data Received From Electric Traction Control Module (Dodge)

Summary of DTC U1108 #

The U1108 diagnostic trouble code (DTC) signals a communication issue between modules on the vehicle’s data bus, specifically relating to the Electric Traction Drive (Inverter). The code appears when the J1850 Serial Communication Protocol (SCP) — an older but still common automotive network standard — detects missing or invalid data from the inverter module. This inverter manages the high-voltage current that drives electric motors in hybrid or electric vehicles. When the vehicle’s control modules can’t reliably communicate with the inverter, system performance and safety could be at risk. Prompt diagnosis is crucial to avoid potential drivability or charging issues.

Common Symptoms for DTC U1108 #

When U1108 is set, the vehicle may exhibit a range of symptoms, some subtle and others more obvious. Communication faults can disrupt the coordination between the powertrain and hybrid/electric drive systems. Look out for these common warning signs:

• Check Engine Light or hybrid system warning lamp illuminated
• Loss of electric traction (vehicle may run on gasoline engine only, if hybrid)
• Reduced power mode or “limp home” operation
• Failure to start in electric mode (for EVs or hybrids)
• Noticeable drivability issues, such as hesitation or jerky acceleration
• Diagnostic tool unable to communicate with inverter module

Probable Causes for DTC U1108 #

The U1108 code is most frequently triggered by interruptions or faults in the data bus or the inverter itself. While the communication protocol (J1850 SCP) is robust, several underlying issues can cause data transmission failures. Here are the most common causes, in order of likelihood:

1. Faulty or disconnected inverter module
2. Wiring harness issues (damaged, corroded, or loose connectors on the data bus)
3. Data bus faults (shorts, opens, or electrical noise on the J1850 network)
4. Faulty Powertrain Control Module (PCM) or Hybrid Control Module
5. Software glitches (requiring module re-flash or update)
6. Electrical interference from aftermarket electronics

Step-by-Step Diagnosis for U1108 #

Properly diagnosing U1108 requires a systematic approach, as communication faults can be elusive. Here’s a proven step-by-step guide, suitable for both advanced DIYers and professional technicians:

• 1. Confirm U1108 presence: Scan all modules with a professional OBD-II/EOBD tool. Check for other communication codes — multiple codes may point to a bus-wide issue.
• 2. Inspect warning lights and symptoms: Note if hybrid/electric system warnings or drivability issues are present.
• 3. Visual check: Inspect the wiring harness and connectors at the inverter module for corrosion, damage, or loose pins. Look especially for water ingress or rodent damage.
• 4. Test data bus integrity: With a multimeter or oscilloscope, check continuity and resistance across the J1850 SCP lines. Look for shorts to ground, power, or open circuits.
• 5. Attempt communication: Try to communicate directly with the inverter module using scan tool. If possible, check for module-specific codes or live data.
• 6. Check for module updates: Consult the OEM’s technical service bulletins (TSBs) for possible software updates or known issues.
• 7. Substitute known-good parts: If wiring and bus integrity check out, consider testing with a known-good inverter or control module if available.

Possible Repairs for U1108 #

Once you’ve identified the root cause, targeted repairs can resolve the U1108 code and restore normal vehicle operation. Here are the most effective remedies, matched to the likely causes:

• Repair or replace damaged wiring or connectors on the data bus or inverter harness
• Clean corroded terminals and ensure secure connections
• Replace a faulty inverter module (after thorough confirmation)
• Repair or replace the PCM or Hybrid Control Module if it’s not communicating
• Update or re-flash module software as per OEM instructions
• Remove or reroute aftermarket electronics causing electrical interference

Can You Drive With U1108? #

Driving with U1108 is generally not recommended for electric or hybrid vehicles. While some vehicles may default to gasoline operation (if hybrid), you risk being stranded if the electric drive system fails completely. Loss of inverter communication can also limit regenerative braking and charging functions. In some cases, the vehicle may enter limp mode or refuse to start. For your safety and to avoid further damage, have the issue diagnosed and repaired promptly.

Vehicles Most Commonly Affected by U1108 #

This code is typically found in hybrid and electric vehicles using the J1850 SCP data protocol. It’s most often reported on models from certain OEMs, especially those using Chrysler/Fiat/Dodge platforms from the early 2000s to mid-2010s. Some examples include:

• Chrysler Pacifica Hybrid
• Dodge Durango Hybrid
• Fiat 500e
• Jeep Grand Cherokee Hybrid
• RAM ProMaster EV (select years)

Common Mistakes & Best Practices for U1108 #

Because communication codes often appear alongside other faults, it’s easy to misdiagnose or overlook the real issue behind U1108. Avoid these common pitfalls and follow best practices for a successful repair:

• Don’t replace the inverter module without verifying wiring and bus integrity first.
• Check for multiple data bus codes before focusing solely on U1108.
• Always disconnect the 12V and high-voltage battery before handling inverter wiring.
• Refer to OEM wiring diagrams and TSBs for updated repair procedures.
• Use a scan tool that can access hybrid/EV modules, not just standard OBD-II codes.

Express FAQ — U1108 #

Here are quick answers to common questions about U1108:

• Q: Can a weak battery cause U1108?
  A: Yes — low 12V system voltage can disrupt module communication and trigger U1108, especially during startup. Always check battery health first.
• Q: Will clearing the code fix the problem?
  A: Clearing the code resets the warning light, but if the underlying fault persists, U1108 will return immediately or on the next drive cycle.