P0521 no oil pressure on gauge

P0521 no oil pressure on gauge — diagnose and fix

Shops are reporting a large number of GM engines with a P0521 no oil pressure on gauge

condition on the 5.3L, 6.0L and 6.2L engines equipped with active fuel management (AFM) systems. The P0521 engine oil pressure (EOP) sensor performance trouble code can be caused by a faulty sensor, a stuck AFM oil pressure relief valve or sludge buildup in the engine. Here’s how to diagnose and fix a P0521 no oil pressure on gauge condition

Test the oil pressure sensor

Locate the oil pressure sensor at the rear of the engine block. Disconnect the electrical connector and then remove the sensor using an oil pressure sensor socket. Next, remove, replace or clean the filter located under the sensor.

Attach a mechanical oil pressure gauge and start the engine. If the oil pressure reads fine on the mechanical gauge, replace the sensor. If the oil pressure is still low or at 0, move on to the next step.

Check oil pressure at the oil filter

Remove the engine oil filter. Attach an adapter and then your mechanical oil pressure gauge. Then run the engine and compare the oil pressure reading to the one from the sensor port. If the oil pressure at the oil filter adapter is good but the pressure reading at the oil pressure sensor is low, that’s the sign of a partially stuck open AFM oil pressure relief valve or sludge buildup in the engine.

If the oil pressure is low at both the sensor port and the oil filter adapter you may have an oil pump issue, a stuck oil pump pressure regulator valve, sludge buildup or an AFM relief valve that’s stuck in the wide open position.

©, 2019 Rick Muscoplat