This DEF pressure limiting unit sheet documents Detroit fault code SPN 4336 / FMI 5 on EPA10 engines, a circuit-failed-open condition that drives a 25% derate. The procedure uses two voltage checks at the limiting-unit connector to separate an open supply wire from a failed component.
Official document details
| Brand | Detroit |
| Model coverage | Detroit DD-Series (DD13, DD15, DD16) and Series 60 (DDEC VI) |
| System / Group | DD Series (EPA 2007-Current) / DTCs |
| Fault code | SPN 4336 / FMI 5 |
| Fault name | Pressure limiting unit circuit failed open |
| Emissions platform | EPA10 |
| Pages | 2 |
| File size | 0.2 MB |
| Format | |
| Language | English |
| Source | TruckFaultCodes.com (© 2017); Detroit Power Service Literature |
DEF pressure limiting unit sections covered
The two-page routine inspects the connector, then reads supply and signal voltages to locate the open circuit.
- Monitored parameter and 25% engine derate; MIL and CEL
- Disconnect the harness connector and inspect the pins
- Read voltage at pin 2 to ground (greater than 11.75 volts)
- Repair the supply wire to ACM2 pin 5 if voltage is missing
- Read voltage at pin 1 (2.25 to 2.50 volts)
- Repair the wire to ACM2 pin 26, or replace the unit
Applicable truck models
These steps cover Detroit DD-Series (DD13, DD15 and DD16) and Series 60 DDEC VI engines on the EPA10 platform with the ACM2 aftertreatment control module. Component detail and removal live in Detroit Power Service Literature at the Detroit Diesel official website.
Who needs this DEF pressure limiting unit manual
Technicians facing a 25% derate with SPN 4336 / FMI 5 need this pressure limiting unit manual to test the harness voltages before replacing parts, since the open can lie in either the supply or the signal wire.
The full 2-page PDF is available in the DiagTechPro manuals library; a free account is required to download. For workshop reference, Detroit documents the matching component removal and installation steps for SPN 4336 / FMI 5 in Power Service Literature, and technicians should keep the wiring pin numbers shown in this sheet on hand while testing on the bench.
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