This SPN 3563 FMI 21 document is a Detroit DD Series fault-code procedure for an ambient and intake manifold pressure difference (high box) on GHG14 engines. It compares manifold pressure to barometric pressure to judge the sensor and the charge air system.
Official document details
| Brand | Detroit |
| Model coverage | Detroit DD Series (EPA 2007-Current) |
| System / group | DD Series / DTCs |
| SPN | 3563 |
| FMI | 21 |
| Condition | ambient and intake manifold pressure difference (high box) |
| Emissions level | GHG14 |
| Source | Detroit Power Service Literature |
| Pages | 3 |
| File size | 0.4 MB |
| Format | |
| Language | English |
SPN 3563 FMI 21 troubleshooting steps
With the ignition on you compare intake manifold air pressure to barometric pressure; a reading outside 0.5 psi calls for a new intake manifold pressure/temperature sensor. The comparison is repeated at idle after starting the engine, and if both pass you perform a Charge Air Cooler inspection and leak test per the vehicle manufacturer literature, then contact the Customer Support Center with the diesel diagnostic tool log file if nothing is found.
- Fault description: ambient and intake manifold pressure difference (high box)
- Steps 1 to 3 – Compare manifold pressure to barometric, key on
- Steps 4 to 6 – Start engine and repeat the comparison at idle
- Step 7 – Charge Air Cooler inspection and leak test
- Customer Support Center and log-file escalation
Applicable truck models
This fault code applies to Detroit DD Series GHG14 diesel engines using an intake manifold pressure/temperature sensor and a Charge Air Cooler. The leak test follows Original Equipment Manufacturer literature; confirm the sensor part against Detroit resources on the official Detroit Diesel website.
Who needs this SPN 3563 FMI 21 manual
Diesel technicians and workshop owners chasing a high-box boost mismatch on a GHG14 Detroit engine use this document to separate a faulty manifold sensor from a leaking charge air system before escalating the case.
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