U1106 — SCP (J1850) Invalid or Missing Data for Legislated Diagnostics #

Note: The description of DTC U1106 may vary depending on the manufacturer (OEM). Always refer to your vehicle’s official service documentation for the most accurate wording.

Known description variations:

• “SCP (J1850) Invalid or Missing Data for Legislated Diagnostics” (Ford, Lincoln, Mercury)
• “Serial Communications Problem – Invalid/Missing Data for Emissions Monitoring” (Mazda)
• “CAN Communication – No Data Received from Emissions Module” (Some GM models)

U1106 Code Overview #

The U1106 trouble code indicates a communication failure on the Standard Corporate Protocol (SCP)—also known as J1850—network, specifically involving data required for legislated emissions diagnostics. The SCP network is a communication bus that allows different modules in your vehicle to exchange information. When a module (often the powertrain control module, or PCM) fails to receive valid or expected data from another module, particularly data needed for emissions compliance, it sets the U1106 code. This is a generic network code, but its impact can vary widely depending on which data is missing or invalid. While it may not always trigger an immediate drivability concern, it often affects readiness for emissions testing and can signal deeper network reliability issues.

Frequent Symptoms for U1106 #

Symptoms for a U1106 code can range from subtle to obvious, depending on which module or data stream is affected. Sometimes, you might notice nothing at all, while in other cases, the vehicle may behave unusually or warning lights may appear.

• Check Engine Light or Malfunction Indicator Lamp (MIL) illuminated
• Emissions test readiness monitors not completing
• Possible no-start or extended cranking (rare)
• Other communication-related codes stored
• Erratic instrument cluster operation
• Unexpected warning messages in the driver information center

Most Likely Causes for U1106 #

The U1106 code is most commonly related to network communication problems. Some causes are more likely than others, but always verify through proper diagnosis.

1. Loose or corroded wiring/connectors at a module or splice junction
2. Faulty control module (often the PCM or a related emissions module)
3. Intermittent or open circuit in the SCP (J1850) communication bus
4. Aftermarket electronic devices interfering with network signals
5. A blown fuse supplying a module on the SCP network
6. Water intrusion or previous accident damage affecting harnesses

Step-by-Step Diagnostic for U1106 #

A systematic approach is essential to nail down the root cause of a U1106 code. Skip no steps, as network issues can be intermittent and elusive.

• Verify the presence of U1106 and note any other codes (especially U-codes indicating network faults).
• Check for active warning lights and run a complete health scan of all modules using a professional scan tool.
• Visually inspect wiring and connectors at all related modules, especially at the PCM and emissions control modules.
• Check for evidence of water damage, corrosion, or pin drag at connectors.
• Test the SCP (J1850) data lines for continuity and proper resistance (typically 60 ohms across the bus).
• Disconnect aftermarket devices (alarms, remote starters, audio systems) that tap into the vehicle’s wiring.
• Check fuses that supply power to networked modules.
• If all wiring passes, use a known-good module to substitute suspected faulty modules one at a time (if practical).

Possible Repairs for U1106 #

The right repair for a U1106 code depends on the specific cause you identify. Always clear the code and retest after each step.

• Repair or replace damaged wiring or corroded connectors on the SCP (J1850) bus
• Replace the faulty control module (after verifying it’s the source)
• Remove or properly install aftermarket electronic devices
• Replace blown fuses and address root causes of fuse failure
• Repair water leaks or harness damage from previous accidents
• Clean and re-seat all network connectors, ensuring tight fit and clean pins

Is It Safe to Drive with U1106? #

Driving with a U1106 code is generally safe in the short term, but not recommended for extended periods. While the code itself may not immediately impact drivability, it often prevents certain emissions monitors from running—meaning your vehicle may fail an inspection. In rare cases, network issues can escalate, leading to more serious problems such as loss of critical data to the PCM or instrument cluster. If additional symptoms appear (like stalling, no-start, or multiple warning lights), stop driving and seek professional help.

Vehicles Most Commonly Affected by U1106 #

This code is most frequently seen on vehicles that use the SCP (J1850) communication protocol, particularly from certain years and manufacturers.

• Ford (Focus, F-150, Expedition, Explorer, Taurus, etc., model years 1996–2010)
• Lincoln (Navigator, Town Car, LS)
• Mazda (Tribute, B-Series trucks with Ford-based electronics)
• Mercury (Mountaineer, Sable, Grand Marquis)
• Some GM models with legacy J1850 systems (pre-2006)

Common Mistakes & Best Practices for U1106 #

Network codes like U1106 are sometimes misunderstood or misdiagnosed. Avoid these pitfalls by following professional diagnostic logic and not jumping to conclusions.

• Replacing the control module without first checking wiring and connectors
• Ignoring aftermarket add-ons that may tap into the data bus
• Overlooking fuse issues that disable an entire module
• Trying to clear the code without addressing the underlying fault
• Not verifying repairs by driving and rescanning for codes

U1106 FAQ Express #

Here are quick answers to some of the most common questions about the U1106 code.

• Q: Can a weak battery cause U1106?
  A: Yes, low voltage during startup can cause network errors. However, the battery is rarely the root cause—verify wiring and module health.
• Q: Will U1106 clear itself after a repair?
  A: Sometimes, but it’s best to clear the code manually with a scan tool and perform a drive cycle to ensure the problem is resolved.