Battery / ECU Power Supply Voltage - Data Valid but Below Normal Operational Range (Most Severe)
The JD-SPN168-FMI1 (John Deere PowerTech) diesel fault code means: Battery / ECU Power Supply Voltage - Data Valid but Below Normal Operational Range (Most Severe). This is a critical severity code.
- Keep driving?
- No -- stop driving
- DIY difficulty
- intermediate
- Estimated cost
- $60-$280 wiring/relay, $180-$450 module -- add dealer diagnostic time ($180-$240/hr in 2026)
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Common Symptoms
- Intermittent code set on load or vibration
- Relay / actuator not responding as commanded
- Operator display warning icon
Probable Causes (Ranked by Likelihood)
- Corroded weatherpack connector on frame harness Very Likely
- Failed relay or open fuse on the output circuit Likely
- Broken wire at actuator strain relief Likely
- Low battery voltage under crank Possible
Step-by-Step Diagnostic Procedure
Confirm system voltage at key-on >12.4V (or 24V on heavy chassis).
Measure circuit resistance end-to-end; compare against Technical Manual (CTM) spec.
Activate the output through Service ADVISOR and watch for expected current draw.
Inspect for rodent damage at the valve-cover pass-through on row-crop tractors.
Frequently Asked Questions
What is John Deere fault code SPN 168 FMI 1?
On John Deere PowerTech engines, SPN 168 FMI 1 means: Battery / ECU Power Supply Voltage - Data Valid but Below Normal Operational Range (Most Severe). Critical code -- stop operating until repaired.
Can I keep using my John Deere tractor with SPN 168 FMI 1?
Critical fault -- do not operate; tow or trailer to a dealer. Diagnose with John Deere Service ADVISOR via an EDL v3 / CF3 interface.
How much does it cost to fix John Deere SPN 168 FMI 1?
Repair cost range: $60-$280 wiring/relay, $180-$450 module -- add dealer diagnostic time ($180-$240/hr in 2026). Dealer labor on large tractors runs $180-$240/hr in 2026.
Sources
This page is built from documented references. Verify against your own service info before repair work.