Intake Air Heater Relay #1 - Current Above Normal or Grounded Circuit
What does JD-SPN729-FMI6 mean?
The JD-SPN729-FMI6 (John Deere PowerTech) diesel fault code means: Intake Air Heater Relay #1 - Current Above Normal or Grounded Circuit. This is a moderate severity code.
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 729 FMI 6?
On John Deere PowerTech engines, SPN 729 FMI 6 means: Intake Air Heater Relay #1 - Current Above Normal or Grounded Circuit. Moderate code -- diagnose soon; continued operation may increase repair scope.
Can I keep using my John Deere tractor with SPN 729 FMI 6?
Moderate fault -- you can usually keep working but expect derate if aftertreatment-related. Diagnose with John Deere Service ADVISOR via an EDL v3 / CF3 interface.
How much does it cost to fix John Deere SPN 729 FMI 6?
Repair cost range: $60-$280 wiring/relay, $180-$450 module. Dealer labor on large tractors runs $180-$240/hr in 2026.