Hey everyone.
My car is a 1988 CSX-T. Recently my check engine light has been coming on for code 52.
Fault Code 52
Synopsis
Description: Oxygen sensor output indicates rich too long
Power loss light: Off
Limp-in mode: Engine allowed to run rich, but prevented from running lean
Possible Causes
Bad oxygen sensor - Replace the sensor which is located on the turbo housing near the down pipe (for turbo) or on the down pipe near the exhaust manifold.Bad connection or wiring - Check the wiring and connections between the sensor and the logic module (or SMEC). Clean and regrease any corroded connectors with dielectric grease and repair any shorts. Look for melted wire insulation near the exhaust manifold. A shorted connection to any positive source will cause this fault code.
High fuel rail pressure - See the Diagnosing Your Fuel System page.
Diagnostic Method
Trigger Parameters
- In closed-loop
- Sensor output indicates rich for more than 715 seconds (11 minutes, 55 seconds)Results If Component Fails
A fault code 52 is stored, the circuit stays in closed-loop, and the logic module will still monitor the oxygen sensor signal. If the condition persists for four times what it took to set the code, the logic module will allow the engine to run rich, but prevent it from running lean.
So far I've changed the 3 wire o2 sensor with a NGK brand from Cindy.
Using a fluke meter we checked the three wires from the o2 sensor and at the SMEC to the appropriate connector pins and my wiring is fine. We got a buzz for all three wires at either end.
And finally we used a fuel pressure gauge on the Schrader valve and my psi was at 48-55ish while the vacuum line to the FPR was unplugged. Fuel pump was replaced about 2 years ago with a walbro 255.
I thought the pump was causing the rich symptom but doesn't the FPR regulate that?
I am stumped here and open to any suggestions. Thank you