SPN 590 / 591 / 592 — Idle Shutdown Timer State / Function / Override Faults
Idle shutdown faults are frequently parameter or interlock related. Verify configuration and related switch status before replacing hardware.
Fault Overview
SPN 590–592 cover idle shutdown timer state, function, and override. Faults indicate the timer is not operating as configured, the override input is implausible, or the function is disabled unexpectedly.
Engine & Platform Coverage
Symptoms
- •Idle shutdown not working
- •Idle shutdown override fault
- •Engine shuts off at idle unexpectedly
- •Idle timer code
- •Shutdown override switch fault
Possible Causes
- 1.Override switch failed or miswired
- 2.Parameter settings incorrect after programming
- 3.Neutral or park switch interaction
- 4.PTO status incorrectly indicating active
- 5.Wiring fault on override circuit
- 6.ECM configuration mismatch
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
5 steps locked behind Technician Mode- 1Step 1 — Monitor Idle Shutdown Status and Timer in Live Data: Monitor idle shutdown status, timer countdown, and all related interlocks (neutral, PTO, park brake) in live data. Identify which condition is preventing correct operation.
- 2Step 2 — Check Override Switch Status vs Actual Position: Monitor override switch status in live data while operating the switch. Confirm the reported state matches the actual switch position.
- 3Step 3 — Verify Neutral, Park, and PTO Status Are Correct: Verify neutral, park, and PTO status are correct and not creating false conditions that affect idle shutdown logic.
- 4Step 4 — Review ECM Parameters for Idle Shutdown: Review ECM parameters for idle shutdown enable, timer settings, and override configuration. Incorrect parameters after ECM replacement or fleet reprogramming are a leading cause.
- 5Step 5 — Inspect Override Circuit Voltage and Continuity: Measure voltage on the override circuit in both states and perform continuity test.
- 6Step 6 — Confirm No Aftermarket Devices Are Forcing Override or Inhibit: Verify no aftermarket devices are pulling the override circuit high or low.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
2 steps locked- 1Correct parameters.
- 2Replace or repair override switch.
- 3Repair neutral/park switch issues.
- 4Address PTO status faults.
Unlock full diagnostic steps, DVOM tests, and repair procedures.
Full Diagnostic Access
Verification steps, preventative measures, severity guidance, and legacy comparison are available in Technician Mode.
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Related Resources
Related Fault Codes
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Summary
Idle shutdown faults are frequently parameter or interlock related. Verify configuration and related switch status before replacing hardware.