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P0443 Diagnostic and Repair Guide for 1997 Mercury Grand Marquis with 4.6L V8 Engine

Model: 1997 Grand Marquis Fault Code: P0443 Posted: 2012-08-08 21:00

Hello. I own a 1997 Mercury Grand Marquis equipped with a 4.6L V8 engine, currently at 259,154 miles. The P0443 trouble code has been present for approximately four years — since the time I first acquired the vehicle. In addition to P0443, I've also experienced persistent codes P0171 and P0174. The Malfunction Indicator Lamp (MIL) was previously burned out and has now been replaced. After replacing the air filter and MIL, only the P0443 code remains. I'm seeking clear, actionable advice on how to properly diagnose and repair this issue. Any insights or recommended steps would be greatly appreciated. Thank you, Toomin

Related fault codes
P0443
Comments (5)
Anonymous 2012-08-09 11:48

Check for 12V at the red wire connected to the purge solenoid. Ensure the solenoid is not open — verify there is current flow when the key is on. Measure voltage on the other wire with the key ON. Then, with the key OFF, unplug the harness and check if the other wire reads ground. These steps help identify whether the solenoid or wiring is faulty.

Anonymous 2012-08-15 16:36

While inspecting under the hood, I found an electrical connector that was unplugged — it was cylindrical and located near the antifreeze tank. After reconnecting it, nine new diagnostic codes appeared. Once I cleared those codes, the P0443 code disappeared. However, since then, the original P0171 and P0174 codes have reappeared, along with a new P1151 code. I plan to clean my Mass Air Flow (MAF) sensor as a next step. Any additional suggestions would be helpful. EDIT: Upon further inspection, I noticed antifreeze leakage on several hoses and another component — this may indicate a cooling system issue that should also be addressed.

Anonymous 2012-08-16 10:43

I strongly recommend stopping the practice of clearing diagnostic codes. Clearing them resets the vehicle's monitoring systems and erases freeze frame data, which is essential for accurate diagnosis. Instead, operate the vehicle normally and re-scan after a day or two to capture real-world driving conditions. This helps identify whether the issue persists under actual use. Also, avoid plugging in unknown connectors randomly — unconnected harnesses are common on older vehicles. Always refer to an official wiring diagram before making any connections.

Anonymous 2012-08-22 07:22

I cleaned the Mass Air Flow (MAF) sensor following recommended procedures, and since then, the P0443 code has not reappeared. However, a new code — P0401 — has surfaced. This was one of the original codes that caused my vehicle to fail emissions inspection.

Anonymous 2012-08-22 07:33

A helpful video walkthrough is available here: https://www.youtube.com/watch?v=vgRk8J0Hlig