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2G Wiring or bad ECU?

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Sylo

Probationary Member
7
0
Mar 30, 2015
Cincinnati, Ohio
Hey everyone, I'm new here and I'm a little stuck.

Long story short, I bought a 97 GS eclipse n/t 420a 5 sod with the engine half built. The head was replaced and guy said the timing was good.

After putting it back together with multiple trips to a upull with all new spark plugs, spark plug wires, coil pack, crank sensor, cam sensor and I replaced the ECM 3 times from junk cars. The current ECM I pulled from a 97 avenger.

Basically I can't get spark to save my life. Grounds are good, fuel to rails, checked all connectors, asd is good, fuel pump primes, all fuses are good.

I checked as much of the wiring as I could under the fuse box and the main bundle. Could I have missed something? Any advice would be appreciated!
 
First make sure your coil works: Coil spark test:
Unplug the coil primary 3 pin connector. Unplug spark plug cable 2/3 from coil and place a long screwdriver in the 2/3 coil's secondary high voltage output terminal (or leave spark plug cables plugged into coil and connect a wire to the spark plug cable end of either plug 2 or 3). Keep screwdriver shank (or the wire) 1/8" from ground metal so a spark can jump across to ground (simulates spark plug gap). Connect a wire from the 3 pin connector's coil side brown wire (use alligator clip on pin) to ground. Connect another wire to battery positive (careful not to touch wire to any metal). Make sure you have gloves on and stand on a dry rubber mat. Now momentarily touch the other end of the battery positive wire to the 3 pin connector's coil side black-red wire (charges coil - may see spark where touching due to high current - normal). Now remove that wire and you should see the spark (> 30KV) jump the gap from the screwdriver shank to ground (may also see small spark where you removed wire - normal).

Now repeat test for coil 1/4. [ie. Move screwdriver to 1/4 coil's secondary. Move ground wire to 3 pin connector's coil side black-blue wire. Repeat touching battery positive momentarily to the 3 pin connector's coil side black-red wire]

If the coil works, next measure the voltage on the 3 pin connector's Harness side black-red wire. While cranking it should be greater than 10 volts.
 
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The coil works, power going to the coil when testing the middle part of the plug from harness, I tried even to bypass the harness.

For the coil plug, I get a constant 12v but nothing in the trigger wires (black and blue / brown) while cranking

when I turn the car to the on position the asd will click twice, I tried bypassing that also but still no dice.

And like I mentioned earlier the ECM makes a whining noise whenever the key is in the on position, it throws no codes at me when doing the key dance.

I'm at a loss right now


EDIT: also when I unplug the moteur 30a fuse and the iac makes a weird crazy clicking whine noise
 
So you did my stand alone coil test and I assume it works then?
Check the ASD output (red-white wire) for +12 volts with key on.
Sounds like you better open up the ECM and locate that whine. Are you sure it's not the ISC that's whining?
 
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Ceck your crank sensor harness make sure it looks clean and is making a good connection.also check for power and ground their and if you have an oscilloscope probe the signal wire for pulses. If it passes all these test than ya I would suspect the ecu or the ecu isn't getting power or ground.
 
Might be the isc, it's behind and under the throttle body.

Asd gets 12v to it.
And the crank sensor harness is also good and gets power to it with a new sensor on it.

Only reason I don't wanna suspect the Ecu is that I replaced it like 3 times, but they were also from upulls, when i unplug relays or the ecu itself it'll throw code 42 at me, that would mean it has power to it right? I also triple checked the grounds and from what i can see there's nothing wrong. I referenced the grounds from a manual I have.
 
I don't know if this might help you but one time I was getting crank but no spark it was bothering the hell out of me and I was not even getting cel so I had no codes to check. I changed the ecu and it drove fine after that, but if you said you replaced it 3x then idk
 
might be Ecu problems.. couldn't think of anything else that would be causing that
 
Here's something to try (measuring cam and crank sensor voltages) to make sure ECU is supplying them properly.
Unplug cam sensor and measure on harness side with key on:
Yellow wire should have 8.5-9.5V
Blue-red should have 4.8-5.2V
Black-green should have continuity (connected: 0 ohms) to ground.

Unplug crank sensor and measure on harness side with key on:
Yellow wire should have 8.5-9.5V
Blue-white should have 4.8-5.2V
Black-green should have continuity (connected: 0 ohms) to ground.
 
Here's something to try (measuring cam and crank sensor voltages) to make sure ECU is supplying them properly.
Unplug cam sensor and measure on harness side with key on:
Yellow wire should have 8.5-9.5V
Blue-red should have 4.8-5.2V
Black-green should have continuity (connected: 0 ohms) to ground.

Unplug crank sensor and measure on harness side with key on:
Yellow wire should have 8.5-9.5V
Blue-white should have 4.8-5.2V
Black-green should have continuity (connected: 0 ohms) to ground.

When I test for continuity it should read 0 ohms on the black-green wires?
 
Ok, so I did the tests and this is what I got:

Cam sensor
Yellow - 8.8v
Blue-red - 4.9v
Black-green - 009 continuity

Crank sensor
Yellow - 8.9v
Blue-white - 4.9v
Black-green - 009 continuity
 
Well that sounds good. So ECU is supplying correct voltages to them. Did the coils pass the stand alone spark tests I told you to do?

Spark gets generated using the following: ECU (called a PCM {Powertrain Control Module} in the 2gNT), coils, cam sensor, crank sensor, spark plugs, spark plug cables, wiring. There is a filter capacitor probably near the coil which you can temporarily disconnect (don't need it for spark) to see if it's causing problems (would cause spark problem if it has partial short however).

The cam and crank sensors must both be working to get spark. While cranking see if you get some voltage on the blue-red and blue-white (must be connected when measuring). Book doesn't say what it should be but it should be pulsing somewhere between 0 and +5V (but not a steady 0 or +5V) - meter will read the average of the pulses.

If you've tested the coils (the way I said), cam and crank sensors, capacitor, that only leaves the ECU and wiring. ECU is always #1 suspect. Since you've swapped it a couple times it may be ok (although from junk cars you can't be certain - internal capacitors go bad with age so they may all be bad). Next thing is wiring. Connections are the key here. Unplug the ECU and examine the connector pins. They must not be bent or corroded, and must be locked in place. Press each pin on both sides to to check for locked in place. Then check connectors on the other stuff (cam sensor, etc).

Also what voltage do you have on the coil's black-red wire while cranking and connected? Also check grounds on ECU.
 
I tested the coil as you said, it works fine, also the cam, crank sensors and spark plugs/ wires are brand new, I'll have to double check to see if they aren't defective.

All connectors are fine, I haven't checked the pins tho so I'll do that today.

And while cracking the coil voltage was reading 11 something.

What exactly does this filter capacitor look like? I don't recall seeing anything around the coil

EDIT: also, how would I check the grounds on the ECM? Are you talking the grounds throughout the engine bay or going into the ECM from harness?

Update: So I unplugged the cam shaft sensor just to make sure the cam was spinning (it is) and when I moved the sensor around while it was plugged in, the asd would click and a whine noise would happen, not like a high pitch whine but more like a noise similar to a fuel pump priming.

im not familiar with the wiring part of cars but I don't see any damage to the wires from the cam sensor harness
 
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Capacitor is usually a silver tin can mounted to the intake manifold driver's side with 1 wire on it.

I'm more familiar with the turbo but the NT book shows ECU pins 10, 47 and 50 should be connected to ground via the harness. Pin 43 connects to ground inside the unit itself. Pin 46 should have +12v on at all times. Pin 6 should have +12v when ASD relay on (key on).
2gNT Pinout: http://www.dsmtuners.com/threads/2gnt-pcm-connector-views.283950/

The ECU or wiring sounds it may be your problem. The only way to test an ECU is to try it in another car (or send it in to be tested). Or try a known good one in your car. Most junk yard ECU's are no good and can't be trusted.

Make sure battery negative large cable goes to body and starter bolt. There also should be a grounding wire from intake manifold to firewall and from ECU case to firewall. Make sure these connections are clean and tight (remove, clean with sandpaper, retighten).
 
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Alright, I checked and re cleaned all the grounds in the engine bay, and for fun I checked them for ohms, the only one that gave me a reading was the one on the firewall that is a flat black box with a few grounds going into it, it read 2.6 ohms.

For the ECM pins, I checked 46 and had a constant 12v

As for pin 6 for the asd relay, I got nada with the key in the on position, and for some magical reason, I'm no longer getting power to the coil on the harness.

I'm tempted to buy a new ECM off eBay or something just to see if it works
 
The ASD relay is turned on by the ECU when the ECU completes a minimal power-up (ECU pin 67 goes low near 0v to activate ASD relay). [The ASD supplies power to most all other engine stuff including the coils.] So the ECU isn't even completing minimal power-up.

Before ordering another ECU make sure you have +12v on ECU pin 20 when key is on and pin 46 all the time or ECU will never power-up. And try to cleanup that ground connection flat box on the firewall - it's one of the ECU's main grounds and could be a problem. Remove bolt and clean it along with wires attaching to it. If necessary (or as a test) create a new firewall ground for those wires to try to get the resistance closer to 0 ohms. As a test before doing anything, try to measure if any voltage drop (with key on) ACROSS that connection from the wire (before the terminal to the bolt - may have to scrape wire clean) to the firewall. If there's too much resistance there when the ECU is powered, a significant (>0.3v) voltage drop may appear there causing problems.
 
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It doesn't sound like your ecm is the culprit, being that you've tried numerous computers and that only around 2% of ecm's actually go bad. A schematic of the ignition system would be very helpful, and go through and test every circuit on the primary side (before the coil) since your coil is no longer firing. May be a little tedious but might save you some money and time in the long run
 
Loose pins in the connector perhaps. Had an issue like this on a Honda Pilot once. It was a no spark issue and I'd gone through fuel pressure test, checked coils then went to pull the ECU to check for any moisture damage. When I looked at the harness real quick on the connector end I'd noticed what looked like a missing pin in the connector but the wire was in place at the backside. I lightly pulled on it and it came out, pin and all. No damage. No corrosion. For some reason the connector itself was just fatigued and would not hold the pin in place. I put the pin in and the ECU and she started up fine. Pulled the pin while running and dead in the water. A little adhesive and sent the car on its way after confirming the pun wasn't moving. Very rare to happen but you never know.
 
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