Author Topic: its dead  (Read 3194 times)

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bumati

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Re: its dead
« Reply #15 on: November 28, 2010, 04:28:43 PM »
Asd?   What is this?

bumati

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Re: its dead
« Reply #16 on: November 28, 2010, 04:30:09 PM »
Left key on for a few minutes. No codes.

Offline Jeffy

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Re: its dead
« Reply #17 on: November 28, 2010, 05:20:16 PM »
Left key on for a few minutes. No codes.
Left the key on?  If your not getting a CEL and Brake light when you turn the ignition on, I would suspect the PCM.  It's supposed to go into diagnostic mode when it stars up.

Also, you should always get some type of code.  You'll get a 12, 33 and 55 always.  If you're not getting any codes then I suspect the PCM is FUBAR.
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Offline 95 Lowbuck

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Re: its dead
« Reply #18 on: November 28, 2010, 06:44:25 PM »
Are you sure you are checking for codes properly? (cycleing the ignition switch 3 times)
By the way great responces on this post.
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Offline sharpxmen

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Re: its dead
« Reply #19 on: November 28, 2010, 07:09:03 PM »
Hmm no CEL and Brake light when starting up?  I believe that's when the PCM goes though it's diagnostic.

if circuit G50 has no power when the key contact is on (key in run position) then the PCM won't go into startup mode, that's the same circuit providing command 12v to ASD and Fuel Pump relays, so he should start by checking that first (it's fuse 5 in the fuse block)

Asd?   What is this?


ASD Relay = Automatic Shut Down relay, is the one that sends power to the coil and fuel injectors while the engine is rotating.

Do the tests i suggested, you might save some money (i'm not saying is not the PCM but you should check this first).

EDIT: the gauges are powered from fuse 9 and both fuse 5 and fuse 9 are in turn powered from the same circuit coming from the key contact. If your gauges are not working with the contact in the run position then could be a problem with your contact, if they are working then check fuse 5 and see if it's fine or not, if it is check the power at the ASD and Fuel Pump relays - if you have 2 prongs with 12v (on each of these 2 relays) with the contact in the run position then you have a different problem (and could mean the PCM is fried but you can't tell for sure), if there's only 1 prong with 12v then it's an electrical issue which you should fix before buying more parts.
« Last Edit: November 28, 2010, 07:22:52 PM by sharpxmen »
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Offline Jeffy

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Re: its dead
« Reply #20 on: November 28, 2010, 07:57:39 PM »
if circuit G50 has no power when the key contact is on (key in run position) then the PCM won't go into startup mode, that's the same circuit providing command 12v to ASD and Fuel Pump relays, so he should start by checking that first (it's fuse 5 in the fuse block)
Yeah, I was looking at the schematic and saw the ASD connected to the fuel pump.  Thought about it but didn't say anything.  Figured you'd mention it.   :lol:
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Offline sharpxmen

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Re: its dead
« Reply #21 on: November 28, 2010, 08:54:14 PM »
Yeah, I was looking at the schematic and saw the ASD connected to the fuel pump.  Thought about it but didn't say anything.  Figured you'd mention it.   :lol:
:thumb:
same circuit that goes to PCM pin 9 also
'95 YJ, NSG370 6spd / Hurst shifter, Dana 300 + 4:1 Doubler / tri-stick, Custom skid, Super D35 / Auburn LSD / 4.88, 35x12.5x15 BFG KM2, 64mm t/b, 1.7 RollerRockers, MkVIII e-fan, Dual Diaph Booster
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bumati

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Re: its dead
« Reply #22 on: November 29, 2010, 07:03:19 AM »
Where is asd?  In the pdc labeled as fuel?

Offline sharpxmen

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Re: its dead
« Reply #23 on: November 29, 2010, 08:09:36 AM »
Where is asd?  In the pdc labeled as fuel?

location "E" in the PDC (NOT labelled as fuel), next to the starter relay

fuel pump relay is in location "B"

the relay slots are lettered from A to G starting at the end with the lock for the cover on the PDC (not the hinge side)

did you check fuse 5 in the fuseblock???
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bumati

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Re: its dead
« Reply #24 on: November 29, 2010, 08:40:45 AM »
All fuses are good.  Gauges have power. 

Offline sharpxmen

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Re: its dead
« Reply #25 on: November 29, 2010, 09:14:15 AM »
All fuses are good.  Gauges have power. 

check the power at the relays then, here's a diagram that would help



the 7 and 22 locations will have 12v at all times (contact off as well)

6 and 21 should have power once you put the key contact on (in the run position) and should also have power when you crank it. check these to make sure you have power.

Once you check these you should check to see if you get command ground on those 2 relays when you crank the engine (cavity 10 on the Fuel pump relay and cavity 25 on the ASD relay). If you don't you can also check pin 9 at the PCM connector (white with yellow stripe wire) also so you know the PCM gets signal for run mode if the relays turn out to have the proper power but no command (ground) signal when you crank the engine.

At this point if you get proper power and ground command signal the problem would be one of the relays (most likely the ASD), if you don't get proper power then trace the problem. If you have power and no command ground signal when you crank the engine check at the PCM on pin 3 (red with white stripe wire) you should have +12v permanent (at all times even with the key out of the contact).

Once you check all these report back and we can move onto checking the voltages and signal at the crank and cam sensors, but let's make sure you have proper voltages on the obvious ones first.

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Offline neale_rs

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Re: its dead
« Reply #26 on: November 29, 2010, 10:13:58 AM »
The check engine light should turn on as a bulb check as soon as you start to turn the key.  This does not depend on anything else, no sensor inputs, nothing, just a bulb check.   So, if it does not turn on it is either: 1) the bulb burned out, 2) the PCM has a bad connection, or 3) the PCM is bad.  I went through this not too long ago and in my case it was the PCM.  I don't have the info here right now but the key is to check power and voltage to the PCM.  If it has power and voltage and you still don't get the check engine light then it is almost completely certain the PCM is bad.

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bumati

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Re: its dead
« Reply #27 on: November 29, 2010, 12:58:57 PM »
Preformed all the tests suggested.  Andy showed with a new ecu.  Everything workd now.  Thank you.  The list is a great it was a big help.

Offline sharpxmen

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Re: its dead
« Reply #28 on: November 29, 2010, 03:10:03 PM »
Preformed all the tests suggested.  Andy showed with a new ecu.  Everything workd now.  Thank you.  The list is a great it was a big help.

so was the ECU dead?
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bumati

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Re: its dead
« Reply #29 on: November 29, 2010, 04:42:33 PM »
Yes as soon as it was plugged in the cel lit up. The new Ecu weighed about twice as much as old one.  Why?