1998 Chevrolet Venture 3.4L P1870 Fault Code: What It Means and How to Diagnose

Hello everyone, I'm looking for help interpreting the P1870 diagnostic trouble code on my 1998 Chevrolet Venture van with a 3.4L engine (90,010 miles). The Service Engine Soon (SES) light illuminated unexpectedly during a drive in Vermont, and I've noticed no change in vehicle performance before or after. I started the trip about one hour prior to the issue and had driven up and down hills. Approximately 30 minutes later, the SES light came on and has remained steady—no flashing. Below is the freeze frame data from my OBD2 scan: - Coolant Temperature: 199°F - Engine RPM: 2,289 - Closed Loop Operation: Active - Long-Term Fuel Trim: +1% (-7.0) - Short-Term Fuel Trim: +1% (-1.6) - MAF (Mass Air Flow): 5.57 lbs/min - MAP (Manifold Absolute Pressure): 25.1 psi - MPH: 66 - Calculated Load: 27.8% - TPS (Throttle Position Sensor): 31.0% I only have a generic OBD2 scanner and software, so I'm seeking guidance on what P1870 means and the next steps for diagnosis. Any insights or suggestions would be greatly appreciated.