P0101, P0128, P0300,P0420 SES Light, power loss

[corndogibm]

Would appreciate some help in diagnosing: Code readout is in that order.

2005 Astro, 208K Miles, V4.3 Cargo

Loss of power going up hills, freeway entrance ramps, van shudders during this time. SES light flashes. The above codes have been reset multiple times and SES light will go back on, even before I get a power loss. Van runs fine in all other cases, runs fine after cresting the hill.

I have replaced OEM AC-Delco plugs, wires, rotor/cap, MAF sensor and gas cap. Engine mounts, Trans mount, and Transmission replaced about 15K ago.

issue has been with the van prior to the Trans rebuilt.







Your input is greatly appreciated!

Kevin

[Blue Bowtie]

101 - Check MAF electrical connector and hire harness.

128 - Check CTS resistance and wire harness. 5 VDC reference signal is common with the MAF, so it makes a little sense. This can also set if a thermostat with the wrong rating is installed. Use a 195°F only.

300 - Is the cap a genuine Delco? Almost all aftermarket caps fail within 5-15K miles due to poor insulation. Is distributor worn? Was the CKP/CMP timing checked?

420 - Likely a weak rear oxygen sensor, but measure signal to verify.

My guess is that most of your operational issues are related to the 300, and something in the distributor itself.