U1424 on 2016 Fiat 500: Implausible Engine Torque Signal Causes and Fixes

What's Unique About the 2016-2016 Fiat 500

For the 2016 Fiat 500 (and its platform-mate, the 500X), this code is strongly associated with known software glitches from the factory. Fiat Chrysler Automobiles (FCA) released multiple Technical Service Bulletins (TSBs) that group U1424 with other transmission-related codes. The primary fix is not to replace a hard part, but to reprogram the Transmission Control Module (TCM) and often the Powertrain Control Module (PCM) and Body Control Module (BCM) together with updated software designed to improve shift quality and fix communication errors.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light (Malfunction Indicator Lamp, MIL) is on
• Transmission warning light is on
• Unable to engage gears or getting stuck in one gear.
• Harsh or erratic shifting, especially harsh 1-2 upshifts.
• Vehicle gets stuck in one gear (limp mode), sometimes with a maximum speed of 30-45 mph.
• Delayed engagement when shifting from Park to Drive or Reverse, especially after a cold start.
• Poor or delayed accelerator pedal response.
• RPM flare at engine start.

Most Likely Causes

1. Outdated Transmission Control Module (TCM) or Powertrain Control Module (PCM) Software 🔴 High Probability → Shop Engine Control Module (ECM) Fiat issued multiple TSBs (e.g., 21-024-15 and 08-010-16) specifically to address this code and related drivability issues by updating module software, indicating a known factory logic error. These bulletins explicitly state the fix is reprogramming.
   How to confirm: A Fiat dealer or a shop with a wiTECH scan tool can check the current software calibration ID in the PCM and TCM and compare it to the latest version specified in the service bulletins. The presence of U1424 alongside codes like P1CC9 or P0335 is a strong confirmation.
   Typical fix: Reprogramming (flashing) the Transmission Control Module (TCM), Powertrain Control Module (PCM), and Body Control Module (BCM) with the latest available software as a complete package. This service typically costs between $150 and $350.
   Est. part cost: $0
2. Failing Transmission Control Module (TCM) ⚪ Low Probability → Shop Transmission Assembly While less common than a software issue, an internal failure of the TCM hardware can cause it to misinterpret data or fail to communicate properly. Heat and vibration can contribute to eventual failure.
   How to confirm: If a software update does not resolve the issue and all wiring is confirmed to be good, the TCM is diagnosed by exclusion. A high-end scan tool may show the module is offline or has internal fault codes that persist after a reflash.
   Typical fix: Replace the Transmission Control Module and program the new unit to the vehicle using a tool like wiTECH. A used TCM may be an option but will require programming.
   Est. part cost: $400-$800
3. CAN Bus Network or Wiring Issue ⚪ Low Probability Damage to the wiring harness between the PCM and TCM can corrupt the signals, leading to communication codes. However, this is less common than the documented software issues for this specific code on this platform.
   How to confirm: Inspect the wiring harness for visible damage, chafing, or corrosion, particularly around the transmission and control modules. A technician can use a multimeter or oscilloscope to test for proper voltage and resistance on the CAN bus circuits at the OBD-II port (Pins 6 and 14).
   Typical fix: Repair the damaged section of the wiring harness or clean corroded connectors.
   Est. part cost: $20-$100

Rare But Worth Checking

• Low or Faulty Battery:

Diagnosis Steps

1. Scan the vehicle for all fault codes in all modules. Note any codes that appear alongside U1424, as they are critical clues.
2. Check with a Fiat dealer or use a professional database to see if TSB #21-024-15 or TSB #08-010-16 (and their revisions) apply to the vehicle's VIN and if the software update has been performed.
3. If a TSB is open, have the TCM, PCM, and BCM reprogrammed to the latest software version. This is the most likely fix. Ensure the shop uses a battery stabilizer during the flash.
4. If the software is already up to date, test the battery and charging system to rule out voltage-related issues.
5. Inspect the wiring harness between the PCM and TCM for any signs of physical damage, corrosion, or loose connections. Pay close attention to connectors at each module.
6. Test the CAN bus network for correct resistance (typically 60 ohms with the battery disconnected) and check for voltage integrity with an oscilloscope.
7. If software, wiring, and battery are confirmed good, further diagnosis of the TCM itself for internal failure is required. This may involve replacement as a final step.

Parts You'll Likely Need

• Transmission Control Module (TCM) Software Update — This is not a physical part, but a service. It is the most common fix specified by Fiat's own Technical Service Bulletins to correct logic errors that cause this code. The service typically costs $150-$350 at a dealership or qualified shop.
  Trusted brands: Mopar (Dealer Service)
  OEM price range: $150-$350
  Aftermarket price range: N/A
• Transmission Control Module (TCM) (OEM #55245644) — In the rare case that a software flash does not fix the issue and wiring is good, the module itself may have failed and requires replacement. This part number is for earlier model years but illustrates the type of component. Programming is required after installation.
  Trusted brands: Mopar
  OEM price range: $400-$800
  Aftermarket price range: $250-$500 (Used/Remanufactured)

Related Codes That Often Appear With This One

• P1CC9 — Stands for 'Unable to Engage Gear' and is listed in the same TSBs as U1424, pointing to a common root cause in the TCM software.
• P1D98 — 'Incorrect Gear Ratio Clutch B or D Defective', another code covered by the same TCM software update TSBs.
• P1DAD — 'Input Shaft-Output Shaft Direction Correlation', also listed in the TSBs for the TCM reflash.
• P0711 — 'Transmission Fluid Temperature Sensor A Circuit Range-Performance', another code frequently addressed by the same TCM software updates.
• P0335 — 'Crankshaft Position Sensor Circuit'. TSBs for the platform-mate Jeep Renegade show this code appearing with U1424, with the fix being a PCM software update, indicating the software has trouble interpreting the sensor signal. A faulty crank sensor can be the 🎬 See this guide on replacing the crankshaft position sensor root cause.
• U0402 — 'Invalid Data Received From TCM'. This code often appears with U1424 and indicates a general communication breakdown, which is typically resolved by the same multi-module software updates.

Technical Service Bulletins (TSBs) & Recalls

• 21-024-15 REV-B: For the 2016 Fiat 500X, this TSB directly lists U1424 - Implausible Engine Torque Signal Received, along with P1CC9, P1D98, and P1DAD, as being resolved by reprogramming the TCM.
🎬 Watch: Diagnosing U1424 and related codes on this platform

Platform-Specific Known Issues

• A series of Technical Service Bulletins, including #21-024-15 and its revisions, were issued by FCA for the 2016 Fiat 500X to resolve U1424 and a host of transmission drivability complaints via a TCM software update.
• TSB #08-010-16 REV D is a more comprehensive update for the 2016 500X that requires flashing the PCM, TCM, and BCM together to resolve U1424 and other issues. This highlights the interconnected nature of the modules.
• The ZF 9-speed automatic transmission (948TE) used in these vehicles is known for its complex software logic, leading FCA to release numerous software updates to refine its performance and fix communication bugs.

Mechanic-Grade Diagnostic Values

• CAN Bus Network Resistance — expected: Approximately 60 Ohms. Failure: A reading of 120 Ohms indicates a missing terminating resistor or an open in the circuit. A reading significantly lower than 60 Ohms suggests a short between the CAN high and low wires.
• CAN Bus Voltage — expected: Approximately 2.5 Volts on both CAN-H and CAN-L when inactive. During communication, CAN-H should rise above 2.5V and CAN-L should drop below 2.5V, mirroring each other.. Failure: Voltages stuck at a specific level or not mirroring each other indicate a short to power, ground, or a faulty module.

Hidden / Shadow Codes Worth Checking

• U1424-00: This is the full code with a symptom byte, confirming 'Implausible Engine Torque Signal Received'. While it doesn't add new component information, its presence is noted in TSBs and confirms the specific fault condition recognized by the module. (see via FCA's wiTECH scan tool or other advanced aftermarket scanners capable of reading manufacturer-specific symptom bytes.)

Scan Tool Commands That Help

• wiTECH, AlfaOBD, MultiECUScan: Proxy Alignment (or Proxi Alignment, Proxi Configuration) — This procedure is mandatory after replacing a major control module like the TCM, BCM, or radio. It synchronizes the vehicle's configuration across all modules on the network. Failure to perform a proxy alignment results in a flashing odometer and can cause communication errors.
• wiTECH, Snap-on, AlfaOBD: Phonic Wheel Relearn / Crankshaft Position Sensor Relearn — After replacing the crankshaft position sensor (CKP), this procedure may be required to synchronize the new sensor's signal with the PCM. Failure to do so can cause the engine to run rough, not start, or set correlation codes.

Wiring & Ground Locations

• Main Battery Ground Strap — Connects from the battery negative terminal to a stud on the vehicle's frame/chassis, typically located directly under the battery and its tray.. A corroded or loose main ground is a well-documented cause of widespread, intermittent communication errors on Fiat platforms, including U1424. It creates voltage drops and electrical noise that can disrupt CAN bus signals, often being misdiagnosed as a failed PCM or other module.
• Gearbox/Transmission Ground — On many Fiat 500 models, a primary ground point is a stud on top of the gearbox housing, often located underneath the clutch slave cylinder.. This is a critical ground point for the powertrain. A poor connection here can directly impact signals between the engine and transmission modules, leading to communication codes like U1424.
• CAN Bus at DLC — At the Data Link Connector (OBD-II port), CAN C High is Pin 6 and CAN C Low is Pin 14.. This is the most accessible point for testing the overall health (resistance and voltage) of the main CAN bus network without having to access individual modules.

Real Owner Repair Stories

• YouTube user Eagle Motors (Dodge Durango with 5.7L Hemi (shares FCA network architecture)) — Check engine light, lack of power, vehicle won't accelerate past 35-40 mph.
  ❌ Tried (didn't work) Initially suspecting a transmission issue due to codes U1424 and P1DD2 (Torque Request Signal From TCM Denied).
  ✅ What actually fixed it The root cause was a faulty camshaft position sensor, which set code P0340. Replacing the camshaft position sensor resolved all codes, including the U1424. This shows that U1424 can be a symptom of a primary engine sensor fault.
• YouTube user Hoopties Garage (2016 Jeep Cherokee with 3.2L engine (platform mate to 500X)) — Limp mode, intermittent reverse gear failure, codes P0018 (Crank/Cam Correlation) and U1424.
  ❌ Tried (didn't work) Dealer replaced all four camshaft phasers and oil control valves for $3,500, but the codes returned the next day., Flashing the PCM did not solve the issue.
  ✅ What actually fixed it The technician discovered the tone ring on the exhaust camshaft had physically slipped/walked out of position. Even though it was off by only a few degrees, it was enough to create a signal conflict that triggered both P0018 and the implausible torque code U1424. Replacing the camshaft itself was the final fix.

When the Usual Fixes Don't Work

• While software updates are the most common fix, U1424 can be a 'symptom' code caused by a primary fault in an engine sensor. In multiple documented cases across FCA platforms, a failing crankshaft or camshaft position sensor (setting codes like P0335 or P0340) was the true root cause. The PCM receives conflicting data from the faulty sensor versus other inputs, flags the resulting torque calculation as implausible, and sets U1424. In these instances, replacing the faulty sensor and clearing codes resolved the U1424 without any software updates or transmission work.