Need help with high EFI voltage problems

[slow440]

I have high voltage (a little less than 5 on the signal return on my MAP and on the green TPS sensor. I think I have a short to my 5v power system but I can't find a diagram that shows what wire should be what voltage.

Any help would be very much appreciated.

On the UP side, I'm almost done! It runs, (badly) and the lift, flares, nv3550, transpher case, hydraulic cluch, exhaust, headers, 1987 mustang engine rebuild and swap are all done!! Shocks and radiator should be in next week.

JT

 

[Broncobowsher]

Probably not a short. Look for a bad ground. Without a ground the signal wire will send reference voltage to the ECM.

 

[justinoshea]

Be careful with that SIG RET. there are many expensive sensors attached to it. SIG RET get grounded at the computer and nowere else (hence it's name). I actually burnt the SIG RET trace off the computer PCB, don't ask how.

unplug all sensors that use SIG RET and check the impeadence to +5.

maybe someone with Probst's book can tell you the puter pin number for SIG RET and 5V REF

 

[slow440]

12v and Power ground?

The less than 5v is now 12v, (charged the battery after i ran it down to 5)
I think i might have shorted the O2 harness but I cannot figure out what the other "Power ground" means? Does it only ground when the power is on?

 

[justinoshea]

If SIG RET is at 12, you will reverse bias the sensors. (12-5 = 7 volts the wrong way). the Barometric sensor will fail and cost you $50.

power gnd is the return path for high current things to chassis GND (like relays, actuators). Sig RET is a ground for only the low current sensors.

My problem that popped 2 Bar sensors and a 2 puters was in the 02 harness. I followed some faulty instruction found on the net

 

[slow440]

THank you, I may have it working now. Ill post results later. Now i just have to figure wich wire is left o2, time it, and fix the egr.

JT

 

[slow440]

MAP is burnt, the voltages are all correct now. Thanks for the help. Now on to the power steering conversion.

JT