Fuel Pressure Regulator - Short Circuit
The CAT-CID1796-FMI6 (Caterpillar) diesel fault code means: Fuel Pressure Regulator - Short Circuit. This is a moderate severity code.
Unverified. We could not confirm this code's definition against freely available manufacturer documentation, so treat the meaning, severity and fix guidance on this page as unconfirmed. Check it against the manufacturer's service information for your exact model and serial range before acting on it. This page is kept out of search engines for that reason, and we are working through this family manual by manual.
- Keep driving?
- Short distances only
- DIY difficulty
- advanced
- Estimated cost
- $300-$4500
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View pilot availability →What Are the Symptoms of CAT-CID1796-FMI6?
- Hard start or extended crank
- Low power, derate
- Black or white smoke
- Check Engine Light
- Stall at idle
What Causes CAT-CID1796-FMI6? (Most Likely First)
- Fuel filter restriction / old filters Very Likely
- HP fuel pump internal wear Likely
- Fuel rail regulator stuck Likely
- Injector internal leak dropping rail pressure Possible
- Air intrusion through supply plumbing or filter housing Possible
Can I Still Drive with CAT-CID1796-FMI6?
Short distances only. CAT-CID1796-FMI6 is rated moderate severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
Frequently Asked Questions
What does CAT CID1796-FMI6 mean?
CAT code CID1796-FMI6 (Fuel Pressure Regulator - Short Circuit) is a moderate-severity fuel system fault. Rail regulator solenoid shorted. Common-rail C15/C13 engines rely on 30,000 psi+ rail pressure; even small supply issues or injector leaks can flag this.
Should I replace the HP pump right away?
No — start with fuel filters and a supply pressure test. HP pump replacement on a C15 is expensive ($3,000+) and often unnecessary. Confirm injector return flow and supply pressure first.
How much to fix CAT CID1796-FMI6?
Filter service is $80-$150. Supply pump replacement is $400-$900. Injector replacement runs $500-$800 each installed. HP pump replacement is $3000-$4500.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose CAT-CID1796-FMI6?
Confirm fault in CAT ET and record commanded vs actual rail pressure at idle and rated.
Change fuel filters and prime system; retest.
Check supply pump outlet pressure with a gauge; must meet HP pump inlet spec.
Test for air intrusion in low-pressure side (clear line).
Perform injector return flow test to identify leaking injector(s).
If supply and injectors test OK, HP pump wear is the likely cause.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J1939-73Application Layer: Diagnostics (defines the SPN/FMI fault-identifier framework)
Which Vehicles Commonly Get CAT-CID1796-FMI6?
- Kenworth T800 with CAT C15
- Kenworth W900 with CAT C15
- Kenworth T2000 with CAT C15
- Peterbilt 379 with CAT C15
- Peterbilt 389 with CAT C15
- Peterbilt 386 with CAT C15
- Peterbilt 387 with CAT C15
- Freightliner Classic XL with CAT C15
- International 9200i with CAT C15
- International 9400i with CAT C15
- Western Star 4900 with CAT C15
- Western Star 5900 with CAT C15
- Kenworth T800 with CAT C13
- Kenworth T660 with CAT C13
- Peterbilt 386 with CAT C13
- Peterbilt 387 with CAT C13
- Freightliner Columbia with CAT C13
- International 9200i with CAT C13
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