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HizAndHerz

Corrected wiring diagrams for EDIS-6 ignition module

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I was going to save this info on my computer for reference but decided to archive it here instead so that others might benefit.

 

The pinouts in the MegaSquirt manuals are incomplete. Note that pin 4 is signal return that runs to the ECU (ground reference for SAW, PIP and IDM), whereas pin 9 is ICM ground. ICM ground should be connected to ground via a 1N4003 diode which is what I found inline on a Ford wiring harness. Here's a blurb from an EDIS reference I found on the internet (link is now dead) that explains the reason for the diode:

 

Since the EDIS ICM and the PCM have different mounting locations, a ground offset of as much as +/- 1.0 volt can exist. The use of an ignition ground allows the PIP, SAPW and IDM signals to be measured as differential signals, referenced to ignition ground. The PCM power and ignition grounds are electrically coupled within the EDIS ICM. The EDIS ICM should not be directly grounded. A grounded EDIS ICM will result in lower peak coil currents because ground impedance difference can affect the coil current feedback loop in the ICM. Grounding ignition ground reduces this impedance and causes a negative shift in the targeted peak coil current.

 

6 Cylinder EDIS module pinout

1 - PIP (EDIS output signal)

2 - IDM (diagnostic signal to ECU)

3 - SAW (ECU spark control signal)

4 - Ignition GND (signal return)

5 - VRS- (crank sensor negative)

6 - VRS+ (crank sensor positive)

7 - VRS shield (crank sensor shield)

8 - VPWR (ignition switched 12 volts)

9 - PWR GND

10 - COIL 1 (coil drive)

11 - COIL 2 (coil drive)

12 - COIL 3 (coil drive)

 

Here's the EDIS-6 wiring diagram that I edited with the corrections:

edis6ew-1.gif

 

Edit: I popped open the lid on the EDIS-6 module and found that all ground pins (4, 7, and 9) are connected together on the circuit board. I can see how long ground wires between the PCM, ICM and the engine might cause ground loop problems, but other than that, I'm a little baffled by the need for the diode on pin 9. It is probably okay to leave it out but just keep wire lengths as short as possible and use heavy gauge ground wires.

 

Here is the pinout of the Dodge coil pack:

DodgeCoilPackPinout.jpg

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HizAndHerz

 

Below is the pin-out for the eight cyl EDIS. Can you tell me what pin is used for the signal return ground? I assume it is pin #7 (does not say it) but when you assume something it can bite you! Also, can I use Pin #2 for a tachometer even though it says diagnostic signal to ECU?

 

Thanks

Danno74Z

 

 

8 Cylinder EDIS module pinout Signal EDIS Module Terminal

 

PIP (EDIS output signal) 1

IDM (diagnostic signal to ECU) 2

SAW (ECU spark control signal) 3

VRS - (crank sensor negative) 4

VRS +(crank sensor positive) 5

VPWR (ignition switched 12 volts) 6

IGN GND 7

COIL 1 (coil drive) 8

COIL 2 (coil drive) 9

PWR GND 10

COIL 3 (coil drive) 11

COIL 4 (coil drive) 12

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For EDIS-8, pin 7 is signal return back to the PCM. It also is used for the VR shield. The shield for PIP, IDM and SAW connects to the PCM.

 

I do not know if IDM will drive the stock tachometer. All of my Z's have stuck or lazy tachometers so I haven't tried hooking anything up yet. Got spare tachs - it's just low on my priority list.

 

There are at least 3 circuits posted at the forums at msefi.com for driving the tach. One uses a diode-or tree, another involves jumpering around the series resistor on the tach input, another uses an transistor to buffer the PIP signal. Here's one thread:

http://www.msefi.com/viewtopic.php?p=168265&highlight=edis#168265

 

I'm sure somebody here on Hybridz with an EDIS setup got their tach working.

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A search at the msefi.com forums reveals that at least one person has wired IDM directly to his autometer tach with success. There is one side effect: the ignition module sends a diagnostic pulse on IDM when the engine isn't running, so when you turn the key to "ON" without starting the engine, the tach will jump around a bit. Then, when you start the car, the tachometer will read correctly.

 

You might consider this a "diagnostic feature". :-)

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While connecting IDM directly to the Autometer tach might work, there is some concern that the tach input might present too much load for the IDM output on the module. In this thread, there's a schematic that shows how to buffer either PIP or IDM before sending it to a tachometer: http://www.msefi.com/viewtopic.php?p=168280

 

The Autometer tach might have a jumper that lets you select the input type. If you can select "high impedance" then the IDM signal could be connected directly to it.

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Just use the tach output on the MS. You need to either use one of the LED outputs, or add a transistor to drive the tach. Adding an extra load to the EDIS module PIP signal is probably not a good idea. If you are going to add extra components, add them on the breadboard area inside the MS V3.

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Just use the tach output on the MS. You need to either use one of the LED outputs, or add a transistor to drive the tach.

Yes, that would work, unless you've already used up the LED outputs like I have. Another option is to use the '921 ignition driver on the V3 board since it usually comes with the kit and isn't used for EDIS.

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I used the circuit that was posted in the thread HizAndHerz mentioned.

 

http://www.msefi.com/viewtopic.php?p=168280

 

It seems to work very well. I built it on my breadboard first and used the stim to test on a spare tach. It worked perfectly. I then built the circuit on a "Prototyping Circuit Board" from Jameco, much like P/N 105152. In fact I bought all of the components from Jameco, they are by far cheaper than Digi-Key or Mouser. I mounted the circuit in the dashboard where my PIP and SAW wire runs along the dash harness, but seperated by an inch or so.

 

The circuit shown in the above thread indicates the 921 could be used. I had the following pic from one of the threads.

 

tachdriver8ol_thumb.jpg

 

I couldn't find where I got the pic by the time I went to build it. So I don't know where the credit is due.

 

I think Z-ya has a good idea too. It actually seems to be a "cleaner" setup.

 

Tim

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I forgot to mention that I still used the 2.2K ohm resistor that was in the stock tach signal wire. The tach circuit I built sends a 12vdc square wave to the tach (the same voltage as the original ingnition coil) so I felt that the resistor was still needed. I did not try it without, since it worked with it. I did not want to fry my tach.

 

Tim

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HizAndHerz

 

Below is the pin-out for the eight cyl EDIS. Can you tell me what pin is used for the signal return ground? I assume it is pin #7 (does not say it) but when you assume something it can bite you! Also, can I use Pin #2 for a tachometer even though it says diagnostic signal to ECU?

 

Thanks

Danno74Z

 

 

8 Cylinder EDIS module pinout Signal EDIS Module Terminal

 

PIP (EDIS output signal) 1

IDM (diagnostic signal to ECU) 2

SAW (ECU spark control signal) 3

VRS - (crank sensor negative) 4

VRS +(crank sensor positive) 5

VPWR (ignition switched 12 volts) 6

IGN GND 7

COIL 1 (coil drive) 8

COIL 2 (coil drive) 9

PWR GND 10

COIL 3 (coil drive) 11

COIL 4 (coil drive) 12

 

I'm coming back to this old post for an update. For 8-cyl, I believe pin 7 ground should be used for signal return to ECM/MS and would also serve as the shield for VR sensor. Then use the 1N4003 series diode between pin 10 and chassis/star ground.

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