Been having an issue now for about 2 weeks, and it's driving me crazy. Basic issue is car starts and runs, but RPMS shoot to 2000-2500, voltage gauge bounces rapidly up/down, MIL light starts to flash, fan's won't turn on.... It was running fine for about 100 miiles , so this an anomaly that has just popped up. Basic info: L67 3800 SC engine and 4t60e Trans from '95 Riviera in an '87 Fiero. Had BIN file created by Ryan at Sinister. Using $5B_TPV5.xdf, $5B_V5.adx. Alternator has been checked out 3 times by different auto stores- all tested OK. Tried 3 PCM's- last one a new one from Autostore. Same results on all PCM's. Tried swapping around MEMCAL's, tried eliminating ZIF socket and plugging directly to Adapter, and tried several different PROMS, including one that worked even before I got one from Ryan.
I've buzzed out every wire on the PCM. I also took voltage measurements via Backprobing all of the PCM connectors, both in "ON" and with the engine running. Voltage readings matched up to the FSM chart, and all grounds measured at less than 1 ohm.
Decided to just try some stuff for investigation.
First discovery is that when the Alt connector is plugged in, Voltage on the "L" pin bounces between 5 and 17 volts ( measured at the alt. Should be 12v. Voltage on the scanner is bouncing between 10 and 25v). RPM's are high-around 2500. If I connect the scanner, RPM's drop to normal (850). If I disconnect the scanner ( Tunerpro , XP Laptop), voltage on "L" drops to 0, RPM's go back up. Also, coolant temp readout on laptop is about 40 degrees cooler than actual. All other sensor data looks to be normal, although the data does jump around a bit(as an example, Coolant temps will vary up / down maybe 5-10 degrees every second, say from 160 degrees to 140, then back to 160). It used to read very steady, and accurately, but I lost my laptop and had to start over again, so no telling what settings I may be missing.
If I drive the "L" pin on the Alternator via a direct line to voltage lamp, charging is steady at about 14.1 V. Voltage on "L" wire ( now unplugged) is 0 ( should be 12v). Connect laptop, and voltage on "L" wire goes to 12V steady ( where it should be), but now ESC error pops up, and MIL light is triggered on. Scanner is reporting voltage at 16-17, while VoltMeter at Alt is showing 14.2v. Disconnect the laptop, and about 3 seconds later the MIL light goes off, and the voltage on the "L" wire goes back to 0. ESC error code disappears.
It is very repeatable that connecting / disconnecting inside Tunerpro ( not disconnecting any wires), causes dramatic change to Alternator charge output wire, MIL light, ESC error, and fan turn on. I'm thinking that somehow the PCM needs a better ground, and is finding a ground through the data line when connected, through the PC, and back.
This may be obvious to some, but I've been looking at this for so long now everything looks like a solution / problem. It feels like a grounding issue, but I'm at a loss as to where else to look, or how to look differently at the grounds, to figure it out.
I also have had to play around a bit with the ADX to get communication. I found that an older version ( for V2.2) had different commands in the Header for Connection and Monitor commands, and I sort of copied those to my version of $5BV5, and was able to get communication (old version had wait for silence commands buried in the macros). It may be that doing this is somehow causing some of these issues, but this is far deeper into Tunerpro than I have delved, and I am truly out of my depths. Any insight into this may also be of help to my issues. I need to fix this anyway, just so I can get good data.
As always, your thoughts are appreciated. I'm running out of things to try....
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