'97 Astro 4.3 Crank/No Start / Short to ground on ECM-1 and ENG-1 circuits
Question asked on YouTube Another great ScannerDanner video!
Short fault on ECM-1 and ENG-2 Burned fuses.
No comm @ DLC(good pwr and ground at DLC)
No pwr to pump
Pump verified good with 12v via test lead @ under hood convience center location
Power to all other circuits good/working
No 5v ref. @ pin 12 (ECM WHITE connector)
No 5v ref. @ pin 4(5v ret.) on VCM(ECM WHITE connector)
No 5v ref @ any sensor
No 12v @ pin 4 (ECM BLUE connector)
12v on pin 21 power B(+)(ECM WHITE connector) coming from ECM-B fuse (not shorted)
Fuel and coolant temp gauges pegged out of range
No scope available
1. What is the difference between ECM-B (pin 21 WHITE connector(good)) pwr feed to computer and ENG-1 (pin 4 BLUE connector(shorted)) pwr. feed to computer? Are different sections of the computer powered by different circuits?
2.How can I test ref circuit (5v) if my ECM circuit is shorted to ground(blown ECM-1 AND ENG-1)? Having a tough time locating short that is showing on both those 2 circuits.
-Unplugged all sensors on affected circuits. Short still shows.
-Used inductive short tool to no avail. Tool indicates point in loom short exists, but inspection shows no short/bare wire/broken wire/touching wire.
- ECU swapped with known good unit. No change.
Failure was instantaneous while running. Have chased all power feeds to sensors on affected (pink) wires on ECM-1 circuit, and still shows shorted. Continuity of all wires on that circuit. Unplugged all ECM controlled components and information sensors on that circuit, still shorted.
I have Mitchell1 diagrams for "engine power" circuits. Oh, btw diagram shows fuel pump ground to frame that is not there on vehicle . <shrug>
Thanks for any help!!
[Last edited Jul 05, 2016 23:05:39]