CAT 62 Fault Code: Engine Injector Cylinder #06 : Erratic, Intermittent, or Incorrect
Engine Injector Cylinder #06 : Erratic, Intermittent, or Incorrect · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 62 (SPN 656, FMI 2) flags erratic, intermittent, or incorrect signal behavior on the cylinder #6 electronic unit injector. The ECM logs the code but keeps energizing the injector solenoid, so the engine keeps running while the fault sits active. Diagnosis centers on injector wiring, connectors, and the injector itself, and the code requires the Fuel System Verification Test to clear.
Medium severity. The engine keeps running on this code because the ECM continues to energize the injector solenoid, so there is no immediate shutdown risk. Left unaddressed it can cause rough running, misfire-like symptoms under load, or injector damage, so it should be diagnosed within the shift rather than ignored.
What does CAT error code 62 mean?
CAT code 62 (SPN 656, FMI 2) means the ECM has detected erratic, intermittent, or incorrect electrical behavior on the circuit for the #6 cylinder Electronic Unit Injector (EUI). These engines fire each injector by having the ECM send a 105 V pulse to the injector solenoid, timed and sized for the current engine load and speed. When the signal the ECM sees back does not match what it expects for that pulse, it logs this code.
Importantly, the ECM does not de-energize the injector when this code sets. It keeps sending the drive pulses to the solenoid, so the engine keeps running, but the underlying wiring, connector, or injector problem can still affect how well cylinder #6 fires.
Because the fault is described as erratic or intermittent, it often will not show up unless the engine is warmed up or under load, so a quick check at idle with a cold engine may not reproduce it.
Common causes of 62
- Failed #6 injector (solenoid or internal injector fault)
- Damaged, corroded, or loose wiring between the ECM and the valve cover
- Damaged or shorted wiring under the valve cover, in the injector harness itself
- Plugged oil outlet port on the exhaust valve rocker arm for that cylinder
How to troubleshoot CAT 62: first checks
- Bring the engine up to normal operating temperature before testing, since injector solenoid problems typically show up when the engine is warmed up and under vibration from heavy load, not at cold idle.
- With the engine at operating temperature, visually and physically inspect the wiring and connectors between the ECM and the valve cover, and the injector harness wiring under the valve cover, looking for chafing, corrosion, or loose pins that could cause an intermittent fault under vibration.
- Check the oil outlet port on the exhaust valve rocker arm for cylinder #6 for blockage, since a plugged port is listed as a possible cause.
- Run or prepare to run the Fuel System Verification Test, since this is the specified procedure for this engine family and is required to clear the code.
- Watch for symptoms while flexing or lightly tapping harness sections near the valve cover with the engine running and loaded, since intermittent wiring faults often only appear under vibration.
How the code clears
The code is logged by the ECM but the injector keeps running normally in terms of ECM control. To clear this code, the Fuel System Verification Test must be performed. No other separate clearing step is listed.
Frequently asked questions
Will the engine shut down when CAT code 62 sets?
No. The ECM continues to energize the #6 injector solenoid and keeps the engine running when this code is active. The code is a diagnostic flag, not a shutdown trigger.
Why does the injector fault only show up sometimes?
The problem is described as erratic or intermittent, and it typically shows up once the engine is warmed up and under heavy load or vibration. Wiring and connector issues especially can hide at cold idle and only appear once the engine is working hard.
What causes CAT SPN 656 FMI 2 on cylinder #6?
Four causes are identified: a failed #6 injector, damaged wiring between the ECM and the valve cover, damaged wiring under the valve cover in the injector harness, or a plugged oil outlet port on the exhaust valve rocker arm.
How do you clear CAT fault code 62?
You have to run the Fuel System Verification Test. That is the specified procedure required to clear this code; no other clearing step is given.
What voltage does the ECM send to the injector solenoid?
The ECM sends 105 V pulses to each injector solenoid, timed and sized for the engine's current load and speed.
Should I check the injector wiring cold or warm?
Warm. Perform inspection and testing with the engine at normal operating temperature, since injector solenoid problems tend to appear once the engine is warmed up and under vibration from load.