Diesel Trouble Codes

P2609 — Intake Air Heater 'A' Circuit High (6.7 Cummins (SCR / DEF))

P2609 on 6.7L Cummins SCR/DEF 2013–present means the PCM has detected voltage in the intake-air grid-heater 'A' circuit above the expected range. The platform…

Updated September 2, 2026

What it means

The PCM monitors the intake-air grid-heater ‘A’ circuit and has seen voltage higher than expected. On 6.7L Cummins SCR/DEF 2013–present the cold-start aid is an intake-air grid heater; the platform has NO glow plugs.1

Most likely causes

  1. Grid-heater relay sticking / failed or wiring short to power causing high circuit voltage — Relay contacts can stick closed or wiring can short, raising voltage seen by the PCM on the heater ‘A’ circuit. Typical on this platform: intake-air grid heater (P2609). NO glow plugs.1
  2. Grid-heater element / harness shorted to power or internal short raising circuit voltage — A shorted heater element or damaged harness can pull the circuit high. Typical on this platform: intake-air grid heater (P2609). NO glow plugs.1
  3. PCM driver / control logic fault interpreting heater circuit voltage high — Internal PCM driver fault or reference voltage issue can cause a high-voltage reading on the heater circuit. Generic definition: PCM detected voltage in intake air heater ‘A’ circuit higher than expected range.1
  4. Grid-heater mounting hardware failure / ‘Bolt of Death’ condition affecting heater assembly integrity — Owner reports link P2609 to grid-heater relay failure and the ‘Bolt of Death’ where the grid-heater plate bolt breaks. Reports of P2609 with intake air heater system failure and parts availability issues. Reports of P2609 as grid heater needing fix and fire concern. Reports of P2609 with bolt holding grid heater deteriorated requiring engine dismantle. Reports of P2609 with relay failure, melted bolt/nut falling into intake manifold damaging engine.23456

How to diagnose

  1. Verify code and freeze-frame conditions; confirm P2609 is present and note ambient temperature/start conditions.
  2. Inspect intake-air grid-heater relay operation and power/ground feeds; check for sticking contacts or short to power.
  3. Inspect grid-heater harness and connectors for chafing, heat damage, or short to voltage; perform visual inspection of heater assembly and mounting hardware.
  4. Measure heater circuit voltage and resistance per service information with ignition off/on and relay commanded; compare to expected values.
  5. Check PCM inputs and reference voltages for the heater circuit; inspect for water intrusion or corrosion at PCM connectors.
  6. If circuit tests normal, evaluate PCM control logic with scan tool bi-directional commands and compare to known-good data.

Parts and tools you may need

Rough cost and difficulty

Costs vary by model year, labor time, and whether grid-heater assembly or wiring/relay is involved. Grid-heater replacement and related harness work can be higher if mounting hardware is compromised.

When to see a pro

If the grid-heater mounting bolt is broken or debris is suspected in the intake, stop diagnosis and have the intake inspected by a qualified diesel technician to prevent engine damage. If PCM replacement or reprogramming is indicated, have it performed by a dealer or qualified shop.

Sources

  1. Curated DTC seed — 6.7 Cummins (SCR / DEF) (curated) ↩︎ ↩︎ ↩︎ ↩︎

  2. NHTSA owner report 11516357 ↩︎

  3. NHTSA owner report 11637713 ↩︎

  4. NHTSA owner report 11634617 ↩︎

  5. NHTSA owner report 11657202 ↩︎

  6. NHTSA owner report 11645067 ↩︎