Scanner Will Not Power Up

fix69vette · Sep 9, 2014

1995 v-6 auto convertible. The scanner will not power up. I had the fault code read. It said temp sensor. I replaced it and noticed it had been replaced just before I bought the car. Took it back to have the code read and scanner would not power up. Then hooked up an actron cp-9550, it created a direct short and wires started melting. The car started and ran as it had but the tach read way low. I pulled the dash and one at a salvage yard. Could not find the exact one but I got the junction blocks and wiring to repair mine. Two of the melted wires went directly to the pcm, ecm, eec or what ever you call the computer.

I have cigarette lighter power and all fuses are good. Car seems to run all right except the cooling fan runs all the time the engine is running. I read that running fan, no scanner power and check engine light is indicative of a bad computer. Does scanner power come thru the computer or is there another wiring problem. Thanks

david

Chythar · Sep 9, 2014

I never had that kind of problem with the 94 V6 I had, so I can't really help you there. Though the scanner I have had its own batteries for power, not sure how your scanner gets its power. As far as the dash wiring, all 1994-1995 dashes can be interchanged. The only difference I am aware of is the wiring for the Mach 460 sound system - a factory installation has the Mach 460 wiring wrapped in the wire loom, while a dealer installation has extra wiring clipped to the wiring harness.

The fan is running all the time could be because of the temperature sensor. If the computer can't read the engine temp I believe it turns the fan on. I'm not 100% sure on that, perhaps someone else can pitch in on that.

I don't know how to test that the computer is running right, sorry.

fix69vette · Sep 10, 2014

Chythar said:
I never had that kind of problem with the 94 V6 I had, so I can't really help you there. Though the scanner I have had its own batteries for power, not sure how your scanner gets its power. As far as the dash wiring, all 1994-1995 dashes can be interchanged. The only difference I am aware of is the wiring for the Mach 460 sound system - a factory installation has the Mach 460 wiring wrapped in the wire loom, while a dealer installation has extra wiring clipped to the wiring harness.

The fan is running all the time could be because of the temperature sensor. If the computer can't read the engine temp I believe it turns the fan on. I'm not 100% sure on that, perhaps someone else can pitch in on that.

I don't know how to test that the computer is running right, sorry.

fix69vette · Sep 10, 2014

Wish I had known the wiring harness were interchangeable. My friends of 40+ years at the local Ford dealership said if they had different tag numbers that they were different. The 94 I pulled the wiring from was a 5 speed, mine is an auto.

Does the temp sensor have voltage to it? There is no voltage to mine

I think the battery in your scanner is for the scanner only. My cousins scanner has battery power to keep the screen on when it is unplugged but the power is supplied by the dlc.

What is the interchangeability of computers? To order one they want a code for the tuning. But would a 94 5 speed work just to see if the dlc power comes thru the computer or is it direct?

But thanks for the reply.

David

jrichker · Sep 25, 2014

Scanners are supposed to have their own battery, so be sure to check the scanner battery before trying to use the scanner.
Pin 16 on the OBDII scanner port is connected to the car battery. Short pin 16 to ground and you will make smoke or blow a fuse somewhere.
See http://en.wikipedia.org/wiki/On-board_diagnostics for more information. The OBDII is a SAE spec, and the SAE specific defined pins are the same for all OBDII equipped cars & trucks. Some of the pins are optionally defined by the auto manufacturer.

The 94-95 V6 uses a very different computer from the 94-95 V8, and the are not interchangeable. The computer wiring harnesses are different as well.

The 94-95 V6 auto and 5 speed computers are also different. Use of a 5 speed computer in an auto transmission car may damage the 5 speed computer.

fix69vette · Sep 27, 2014

Chythar said:
I never had that kind of problem with the 94 V6 I had, so I can't really help you there. Though the scanner I have had its own batteries for power, not sure how your scanner gets its power. As far as the dash wiring, all 1994-1995 dashes can be interchanged. The only difference I am aware of is the wiring for the Mach 460 sound system - a factory installation has the Mach 460 wiring wrapped in the wire loom, while a dealer installation has extra wiring clipped to the wiring harness.

The fan is running all the time could be because of the temperature sensor. If the computer can't read the engine temp I believe it turns the fan on. I'm not 100% sure on that, perhaps someone else can pitch in on that.

I don't know how to test that the computer is running right, sorry.

Thank you, Chythar, the temp sensor comment made me do some thinking and I remembered some thing about a wiggle test. I back probed the sensor wires and had continuity but thought there should be power to the sensor and began working back along the wires. With the engine running, I wiggled the wiring and the engine rpm changed and with more wiggling the engine died but started right back up. I started pulling the split poly loom and tape off and found near the intake, one wire that was severed as as if it had been cut. This is inside untouched factory wiring loom. Fan works properly and no service engine light. I do not dare plug in a scanner yet. However, on to another problem in a new thread.

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