International ProStar MaxxForce 13 SPN 1209 FMI 4 EBPS Low Voltage

Question

My 2013 ProStar just popped a solid yellow MIL and I am seeing SPN 1209 FMI 4 on my ServiceMaxx software. The Exhaust Back Pressure sensor reading is stuck at atmospheric pressure and does not fluctuate when I rev the engine. Performance feels a bit sluggish and I am worried about it triggering a derate during my next haul.

garagegrease · Accepted Answer

Found the issue. Specifically, the wire was chaffed about 4 inches back from the EBPS connector inside the convoluted tubing. After splicing in a new pigtail (Part # 2501107C91) and clearing the codes, the sensor responded immediately to throttle input. Total fix cost was about $65 for the pigtail and an hour of shop time.

obd2_owl · Answer

These MaxxForce engines are notorious for rubbing the harness near the lift bracket on the top of the head. Carefully inspect the loom for any spots where the insulation has worn through to the wire.

Rachel Nguyen · Answer

FMI 4 usually indicates the signal voltage is below the normal range, often a short to ground. Check your 5V reference circuit at the sensor plug to make sure the ECM is actually sending power to that rail.

Brian O'Connor · Answer

I've had several of these where the tube itself looks okay from the outside but is rock hard with carbon inside. If the sensor can't see the pressure changes, the ECM might interpret the lack of signal movement as a circuit rationalization fault or low voltage depending on the specific calibration.

International ProStar MaxxForce 13 SPN 1209 FMI 4 EBPS Low Voltage

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