Volvo D8H - SPN 3720 FMI 0 - DPF Excessive Soot and Transmission Shift Inhibited

Question

My 2014 VNM is stuck in derate and won't shift out of 2nd gear after the DPF light started flashing. The dash is showing SPN 3720 FMI 0 and I cannot get a parked regen to start through the stalk or the tool. It feels like the truck is stuck in a safety mode because the soot load is calculated way too high.

backyard_bart · Accepted Answer

The issue was a failed Aftertreatment Hydrocarbon Injector (Part #21407309) that was completely carboned over, preventing the DPF from heating up. I replaced the injector, cleaned the diffuser port, and used Volvo Premium Tech Tool to perform a 'Service Regeneration' which requires a password to bypass the 3720 FMI 0 lock. After a 45-minute burn, the pressure dropped to 0.4 psi at idle and the shift inhibit cleared. Total cost for the injector and the software license time was about $650.

Kevin Tran · Answer

When FMI 0 hits on 3720, the MCM/ACM thinks the filter is at risk of an uncontrolled thermal event. You usually can't force a regen once it hits this stage without clearing the soot load tables first using Premium Tech Tool.

Chris Donovan · Answer

The transmission inhibit is a standard safety feature for Volvo I-Shift when the soot level reaches 'Zone 3' or higher. You need to verify if your 7th injector (hydrocarbon injector) is actually spraying fuel; if the line is restricted, the DPF will never hit temp and just keep loading up.

Rachel Nguyen · Answer

Check your differential pressure sensor (Delta P) tubes. If the tubes are rusted through or leaking, the ECM gets a false high pressure reading and will throw the 3720 code even if the filter isn't actually plugged.

Volvo D8H - SPN 3720 FMI 0 - DPF Excessive Soot and Transmission Shift Inhibited

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