International SPN 8064 FMI 12: Crankshaft Position Signal Inactive
SPN 8064 FMI 12 (FMI 12) — Engine Crankshaft Position - Bad Intelligent Device or Component (Signal Inactive)
Quick Answer
SPN 8064 FMI 12 means the ECM has completely lost the crankshaft position signal, causing a genuine no-start condition. It's a Critical fault - check the sensor connector and mounting before assuming a full sensor failure.
Critical — Stop Engine / Derate Risk
SPN 8064 FMI 12 on an International A26 means the ECM lost the crankshaft position signal entirely, not just a degraded reading. Without a valid CKP signal the engine can crank but will not fire - this is a genuine no-start condition, not a performance complaint.
Overview: International SPN 8064 FMI 12
ProfessionalDieselRepair.com treats this A26 no-start pattern as a connector-first diagnosis - a surprising number of these turn out to be a pushed-out pin rather than an actual failed sensor.
Repair Snapshot
Time
1 - 3 Hours
Difficulty
Intermediate
Parts Cost
$80 - $400
Dealer Labor
$450+
Tools Required
- Scan Tool with Live RPM Data
- Multimeter
- Feeler Gauge
- Snap-on NEXIQ USB-Link
What SPN 8064 FMI 12 Means
SPN 8064 FMI 12 on an International A26 means the ECM lost the crankshaft position signal entirely, not just a degraded reading. Without a valid CKP signal the engine can crank but will not fire - this is a genuine no-start condition, not a performance complaint.
Symptoms Drivers Notice
- Engine cranks normally but will not start
- No RPM reading on the dash during cranking
- Check engine light illuminated with the ignition on before cranking
- Possible history of intermittent stalling before the sensor failed completely
Most Likely Root Causes
Corroded or damaged CKP sensor connector
CommonAn electrical/wiring fault, not a sensor failure - a pushed-out pin or corrosion can completely interrupt the signal path even with a healthy sensor.
Sensor worked loose from its mounting bore
OccasionalA mechanical installation issue where vibration or improper reinstallation after service increased the air gap beyond the sensor's detection range.
Internally failed (open) CKP sensor
OccasionalA genuine sensor hardware failure confirmed by an out-of-spec resistance reading.
Damaged crankshaft target wheel
RareA mechanical engine component failure where the toothed wheel the sensor reads has physical damage, which is a more involved repair than the sensor itself.
Common Misdiagnoses (Don't Waste Parts)
Replacing the CKP sensor without checking the connector and mounting first
Why it happens: A no-start with a named sensor fault feels like an obvious swap.
Do this instead: This is a parts-cannon move on a fault that's frequently a connector or mounting issue - check those first since they're far cheaper to fix.
Overlooking a related camshaft position sync fault that points to the real issue
Why it happens: Techs focus on the most prominent fault code and miss companion codes.
Do this instead: Always pull the full fault list - a camshaft sync fault alongside this one can redirect the diagnosis toward a timing component issue.
Master Tech Commentary
Mechanic's Notes
ProfessionalDieselRepair.com note: don't assume a CKP no-start always means a bad sensor. Check the connector and mounting first - a pushed-out pin or a sensor that's backed out of its bore from vibration is a common, cheap fix compared to a full sensor replacement.
Step-by-Step Diagnostic Procedure
- Step 1: Confirm the no-start by watching for an RPM signal on the dash cluster while cranking - zero RPM confirms the ECM isn't seeing crank position at all.
- Step 2: Connect a scan tool and check for SPN 8064 as an active fault along with a related camshaft position (SPN 8021) sync fault, since these two often appear together.
- Step 3: Inspect the CKP sensor connector for corrosion, a broken locking tab, or a pushed-out pin, which are common causes of a totally lost signal versus a degraded one.
- Step 4: Check the sensor's air gap to the crankshaft target wheel, since a sensor that's worked loose or been improperly reinstalled after service can lose signal entirely.
- Step 5: If the connector and air gap check out, test the sensor's resistance value against OEM specification, since an internally open sensor produces this exact fault.
Professional service / OEM-level scan tools are recommended before clearing this fault for good.
Live Data & Freeze-Frame Tips
Since the signal is inactive rather than erratic, live data won't show a degraded waveform - focus on continuity testing at the connector and verifying sensor resistance against spec rather than trying to log a live signal that isn't present.
Safety Warnings
- Disconnect the battery before working on crankshaft sensor wiring to avoid accidental cranking.
- Be cautious of hot exhaust components near the sensor location if the engine was recently run.
When to Limp In vs Tow
The truck cannot be driven with this fault active since it won't start - arrange a tow or mobile repair rather than attempting extended cranking, which can drain batteries and strain the starter.
Prevention Tips for Fleets & Owner-Operators
- Inspect CKP sensor connectors for corrosion at scheduled PM intervals.
- Verify proper sensor air gap any time it's removed for service.
- Address any intermittent stalling promptly, since it can be an early warning of a developing CKP signal problem.
Related Fault Codes
SPN 8021 FMI 2
A camshaft position sync fault that frequently accompanies a lost crankshaft position signal on the same no-start event.
SPN 636 FMI 2
A related crankshaft position sensor fault seen on other J1939-compliant heavy-duty platforms.
Frequently Asked Questions
Can I keep driving with SPN 8064 FMI 12 active?
No - this fault causes a genuine no-start condition, so the truck can't be driven at all until the signal is restored.
How do I reset this code without a scan tool?
A battery disconnect won't fix the underlying signal loss - the engine simply won't start again until the sensor, connector, or wiring issue is physically repaired.
What triggers this fault?
The ECM sets this code the moment it stops receiving any crankshaft position signal during a crank attempt, rather than after a countdown or threshold like many other faults.
Is this always a bad sensor?
No - a corroded or pushed-out connector pin is a very common and much cheaper cause than an actual internal sensor failure.
How much does this repair typically cost?
A connector repair often costs under $150. A full sensor replacement typically runs $250-$400 including labor.
Why did my truck stall a few times before this happened?
Intermittent stalling can be an early warning sign of a CKP sensor or connector that's degrading before it fails completely and causes a full no-start.