SPN 2630 FMI 2 — Charge Air Cooler Outlet Temperature Data Erratic
Erratic CAC outlet temp is sensor or harness integrity first. Intermittent derates from unstable charge-temp inputs are the most documented pattern. The FSM stabilizes sensing before cooler package replacement.
Fault Overview
SPN 2630 FMI 2 indicates CAC outlet temperature signal erratic or implausible. Failing sensor, intermittent harness, connector fretting, and moisture intrusion are the primary causes. Intermittent derates from unstable charge-temp inputs are a documented pattern. Replacing the CAC or charge-air system components for a sensor or harness fault is the most documented misdiagnosis pattern.
Engine & Platform Coverage
Symptoms
- •CAC temp sensor intermittent
- •Charge air temp fluctuating
- •Erratic boost air temperature
- •Intermittent derate from charge temp
- •Power loss heat soak from erratic CAC temp
Possible Causes
- 1.Failing sensor — failing CAC outlet temperature sensor producing unstable readings
- 2.Intermittent harness — intermittent harness producing unstable signal
- 3.Connector fretting — connector fretting at charge pipe or CAC outlet producing intermittent signal
- 4.Moisture intrusion — moisture intrusion producing short circuit
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
3 steps locked behind Technician Mode- 1Step 1 — Wiggle Test: Perform a wiggle test on the sensor connector and harness. Monitor the CAC outlet temperature PID while wiggling the harness. A PID dropout during the wiggle test confirms a harness intermittent. Inspect the sensor connector on the charge pipe and CAC outlet for chafe at clamps.
- 2Step 2 — Continuity Check: Check continuity through the sensor circuit. Verify continuity and compare against IAT and ambient plausibility. A continuity fault confirms a harness or connector fault.
- 3Step 3 — Sensor Replace After Proof: Replace the sensor after proof of sensor failure. Confirm the harness and connector are clean before sensor replacement. A sensor replaced without proof may replace a good sensor into a harness fault.
- 4Step 4 — CAC Efficiency Evaluation Only If Values Are Stable But High: Evaluate CAC efficiency only if values are stable but high. A stable but high CAC outlet temperature confirms a true thermal event that requires CAC efficiency evaluation. A CAC efficiency evaluation performed before sensing proof may miss a sensing fault.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
2 steps locked- 1Repair harness if intermittent is confirmed.
- 2Service connector if fretting or moisture is confirmed.
- 3Replace sensor if failure is confirmed after circuit proof.
- 4Evaluate CAC efficiency only if values are stable but high after sensing proof.
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.
Start Diagnosing This Fault Now
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Summary
Erratic CAC outlet temp is sensor or harness integrity first. The AI Diesel Tech FSM stabilizes sensing before cooler package replacement.