Injection Actuation Pressure Below Normal
The CAT-CID164-FMI1 (Caterpillar) diesel fault code means: Injection Actuation Pressure Below Normal. This is a serious severity code.
- Keep driving?
- No -- stop driving
- DIY difficulty
- advanced
- Estimated cost
- $400-$3500
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Common Symptoms
- Hard start, long crank, especially when hot
- Low power, black smoke
- Engine may stall at idle
- No-start on some HEUI engines
Probable Causes (Ranked by Likelihood)
- High-pressure oil pump worn (HEUI engines) Very Likely
- Injector cup / o-ring leak allowing oil loss from high-pressure rail Likely
- IAPR stuck open, dumping pressure Likely
- Low engine oil level or wrong viscosity Possible
Step-by-Step Diagnostic Procedure
Connect CAT ET and confirm the active fault; note HEUI actuation pressure live value.
Inspect IAPR connector and wiring at front of engine for damage.
Measure HEUI actuation pressure with CAT ET during cranking; spec ~870 psi at cranking for start.
If pressure is low at cranking, test HP oil pump and check injector cup seals for oil loss.
Replace sensor, IAPR, or pump as indicated by tests.
Frequently Asked Questions
What does CAT code CID164-FMI1 mean?
CAT code CID164-FMI1 (Injection Actuation Pressure Below Normal) is a serious-severity fault in the HEUI injection system. HEUI injection actuation pressure too low. High-pressure oil pump, IAPR, or oil leak. HEUI (Hydraulically actuated Electronically controlled Unit Injectors) uses high-pressure engine oil to fire injectors, so HEUI faults often trace to oil pump wear, oil leaks, or sensor failures.
Can I drive with CAT CID164-FMI1?
No. HEUI faults typically cause hard start, no-start, or derate. Continued driving risks stranding. Tow to a CAT-capable shop.
How much does it cost to fix CAT CID164-FMI1?
Typical cost is $400-$3500. Sensor or IAPR replacement is at the low end; high-pressure oil pump or injector work is at the high end and usually requires CAT dealer-level diagnostic time.
Sources
This page is built from documented references. Verify against your own service info before repair work.