Volvo D13 - MID 128 SID 232 FMI 4 Low Voltage on 5V Sensor Supply

Question

My 2014 VNL is throwing a MID 128 SID 232 code and the dash is lighting up like a Christmas tree. The engine stays in derate and I have multiple sensor errors for the oil pressure and crankcase pressure at the same time. It feels like a short in the harness because it happens more often when it is raining or humid outside.

obd2_owl · Accepted Answer

The issue was the fan clutch speed sensor harness. The wiring had rubbed through against the fan shroud bracket, grounding out the 5V reference circuit share by the EA connector group. I cut out 4 inches of damaged wire, heat-shrunk new 18-gauge leads, and rerouted the loom with heavy-duty zip ties to prevent future rubbing. Total cost was just shop supplies and 3 hours of diagnostic time, and the MID 128 SID 232 code cleared immediately after cycling the key.

Luis Hernandez · Answer

Check your harness rub points near the back of the cylinder head. The EA connector pin 3 feeds several sensors including the EGR position and oil pressure, so if any of those wires are chafed to the block, it will pull the whole 5V rail down to 0V.

Ashley Park · Answer

You need to unplug sensors one by one while monitoring the voltage on the reference line with a multimeter. If the code goes inactive when you unplug a specific sensor, that component is shorting out the loop.

dieselmike88 · Answer

Since you mentioned moisture, pull the engine ECU connectors and check for green corrosion. If coolant has wicked up through the injector harness (common on D13), it can bridge the pins at the ECM and cause SID 232 supply issues.

Volvo D13 - MID 128 SID 232 FMI 4 Low Voltage on 5V Sensor Supply

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