Re: Weird observation during EEC-V code extraction
Not sure why you're not getting 'Slow codes', but your EVP stands for EGR Valve Position, 334 being your closed-valve voltage is higher than expected. sounds like the sensor on the end of the EGR valve is suspect. They are available as separate items. Two tests you can do here:
1. EVP resistance: Key off, disconnect EVP sensor connector. Connect ohmmeter to connector at EVP SIG and VREF (look at your workshop manual for correct wire colour codes). Disconnect vacuum line to EGR, connect vacuum pump and increase vacuum. You should get 5500 ohms to 100 ohms as vacuum increases to 33kPa (10 in. Hg). If not, EGR or EVP sensor may be faulty.
2. VREF at EVP Sensor: Key off, disconnect EVP sensor connector. Key on, measure voltage at vehicle side of harness between VREF and SIG RTN. You should get 4 to 6 volts DC. If not, wiring or EEC-V module may be faulty.
Your 157 (MAF Sensor circuit below minimum voltage) sounds like your MAF sensor is faulty. With the MAF connected and engine idling, backprobe the MAF connector between MAF SIG and Ground - you should get between 0.6 and 1.2 volts DC - if not, sensor maybe faulty. I had this on my Mustang a few years ago - at idle, I was only getting 0.05 vdc (about a tenth of what I should have had as a minimum)! No wonder I was seriously down on power.
I hope these checks reveal something concrete for you to go on.
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