Coil-Wire Connection Issues on 2024-Up Gen 2 Touring Models
ThunderMax technical support has observed coil-wire harness connection issues on some 2024 and later Harley-Davidson® Gen 2 Touring models. This concerns the motorcycle’s factory Harley-Davidson ignition components and has also been observed on stock motorcycles, including motorcycles that have never been on a dyno.
Backfiring, sudden power loss, occasional stalling or poor combustion under load can point to an ignition problem. Inspect the coil-wire harness connection and coil condition early in the troubleshooting process, even when the symptoms appear to be related to tuning.
View / Download the Coil-Wire Technical Bulletin — PDF
Common symptoms
A damaged coil-wire harness, deteriorating connection or weak coil may contribute to:
- Backfiring
- Sudden loss of power
- Occasional stalling
- Poor combustion during acceleration or under heavy load
These symptoms alone do not confirm a coil problem. Inspection and testing help identify the cause.
Inspect the coil-wire harness connection
The ThunderMax technical support bulletin identifies a factory-installed zip-tie that can hold the harness in a bind at the coil connection.
With the motorcycle switched off, locate the connection shown below. Inspect the harness for strain or visible damage. Remove the factory zip-tie identified in the bulletin to relieve the bind.
Highlighted area: the coil-wire harness connection discussed in the technical bulletin.
Watch the coil-wire connection video
Use the accompanying TMax Tech Tips video as a visual reference when locating and inspecting the connection.
Watch “Coil Wire Connection — TMax Tech Tips”
Check coil condition and resistance
Harness strain and weak coil output are separate diagnostic concerns. Relieving strain at the connector does not establish that the coil itself is functioning correctly.
A coil can weaken internally even when its housing and wiring appear normal. For the affected 2024-up Harley-Davidson Gen 2 Touring application, the confirmed resistance values in the ThunderMax technical support bulletin are:
- Primary resistance: approximately 3.5 Ω.
- Resistance at the plug-wire connection towers: above 10,000 Ω.
A noticeably lower reading at the plug-wire connection towers may indicate internal coil deterioration. Have a qualified technician perform the test if you are unfamiliar with the required connections or measurements.
Why ignition problems can resemble tuning problems
With ThunderMax installed, a weak or inconsistent spark can contribute to unstable air/fuel-ratio readings, uneven idle, sluggish acceleration and difficulty maintaining consistent closed-loop operation.
Because these symptoms can resemble a calibration issue, inspect the ignition system early in the diagnostic process. Identifying a harness, connection or coil problem can help avoid unnecessary tuning changes.
Need help troubleshooting?
Contact ThunderMax technical support or email support@thunder-max.com.
Include your motorcycle’s year and model, ECM part number, relevant modifications, and a description of when the symptoms occur. Include your map number and software/firmware versions if available.
Based on the ThunderMax “2024-UP Coil Wire TSB,” version 1.7, dated October 27, 2026.
