Good afternoon all, haven't posted in several years but the time has come to seek help. Sorry for the length but I am trying to give as much info as I have on my issue and what I have already done. Recently acquired a 99 Chevy Silverado 1500 5.3 truck. Other than a loud exhaust, it runs fine for it's age. My issue is that when going uphill, the engine stumbles but will smooth out if I give it more gas. I am using a Zurich ZR11s OBD scanner (Hobo Freight) and do not get any codes. But, when I run the scan under enhanced mode, I generally get 40 or more codes. Check it again after driving it and it drops to maybe 6-8 codes but then reverts back to the same 40 or more. but still no CEL. The codes are mainly circuitry type codes and I will list them at the end of this. Checked the fuel pressure and it was barely hitting 48 psi (spec is at least 52). Changed out the fuel filter, fuel pump and fuel pressure regulator and get good pressure but the stumbling continues. If I pull the vacuum hose off of the Fuel Pressure regulator, the stumbling stops. I have also changed out the MAF sensor as it was reading below specs. All the other sensors are testing in spec. O2 sensors have been replaced and monitoring them indicates the passenger side catalytic is bad. My fear is that the PCM is failing. The common codes are of low voltage, high voltage, insufficient activity etc at the same sensor. This series occurs on several sensors. Any ideas or suggestions are appreciated. Enhanced codes as follows:
P0101-MAF performance
0108-MAP high voltage
0117/ 0118-engine coolant circuit high/low
0121-TP insufficient activity
0125-engine coolant excessive time to closed loop
0131-0135-O2 sensor B1S1 low/high voltage, slow response, insufficient activity, heater performance
0137-0141-same as above but for B1S2
0151-161-same as above for B2S1 and B2S2
0171-0175-fuel trim rich/lean on B1 and B2
0200-injector control circuit
0300-misfire detected
0325-knock sensor system
0327-knock sensor circuit
0332-knock sensor circuit rear
0335, 0336, 0341, 0342, 0343-camshaft position sensor circuit/performance
0401-EGR flof inefficient
other codes randomly appear but do not always come back (evap system, transmission, etc)
Again, any help, guidance or suggestions are appreciated.
, 0138, 0140, 0141, 0151-015
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