Making a bench harness

Technical information, definitions, advice, and support for factory ECU remapping, aftermarket systems, and much more.
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WytWun
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Making a bench harness

Post by WytWun »

Making a bench harness is not particularly hard.

You do need to acquire a set of ECU connectors with as much remnant loom as possible - at least 75mm, but 100mm or more makes it easier. I would recommend removing unneeded pins from the connectors just to make it easier to keep track of which pins you actually have wired, especially with the auto ECU connectors. A thin narrow rigid probe is required to depress the locking tab on each pin so that it will come out. If using an OpenPort 2.0, you can make the reflash connector out of a 2.5mm mono audio plug (I got mine from Jaycar) so that it plugs directly into the OP without the extra reflash connector. Otherwise make sure to get a reflash connector in addition to the ECU connectors.

In the following list of pin numbers, (A) means an auto ECU and (M) means a manual ECU. These pin numbers should be correct for all 3rd gen Magna/Verada and MY2000 onwards Australian made USDM Diamantes.

ODB2 socket wiring:
pin 1 to ECU pin 84(A)/56(M) - wired in the OpenPorts so I included it, not sure if req'd
pin 4+5 to ground
pin 7 to ECU pin 85(A)/62(M) - K-line
pin 16 to 12V - unswitched

ECU pins:
ground: 42, 48, 76, 88, 97 (A) / 13, 26, 91 (M)
battery backup: 66(A)/80(M) - connect to 12V unswitched
+12V (switched): 41, 47, 77, 89 (A) / 12, 25 (M)
Ignition: 98(A) / 82(M) - +12V = Ignition ON; disconnected = ignition OFF
reflash: 113(A) / 79(M)
CEL: 22(A) / 36(M) - wire lamp from 12V to this pin

TCU reflash on H8 ECUs only: 114 (A)

Notes:
- I ran the ignition pin and the switched +12V pins (which are normally fed via the engine and A/T control relays) from a single switch; for reflashing it would probably be okay for these pins to be wired unswitched as for battery backup pin.
- I found a LED pre-made with series resistor for 12V use in AutoPro (Narva brand) - red pigtail to +12V and yellow pigtail to CEL pin. CEL should be lit while ignition is ON; off otherwise (may come on briefly when power first applied to battery backup line).
- I made the power connection a cigarette lighter plug. I normally run it with a mains powered 13.8V power supply via leads to a cigarette lighter socket, but have successfully used it in-car (on a J ECU, I wouldn't attempt this with an H or earlier ECU).
- I was able to get a female OBD2 (diagnostic) connector with about 300mm of flying lead from an Ebay seller; the wires are very fine though and needed lots of care with joining to avoid breakage.
- I used a 12-way "chocolate block" screw terminal strip to wire it all together.
- H8 ECUs with integrated TCU (late F/H Magna/Verada, MY2000 USDM Diamante): the TCU function can be reflashed using pin 114 (this pin not used on SH2 ECUs) instead of pin 113.
- MY1997 & MY1998 USDM Diamantes have separate ECU and TCU units so pin/connector information in this post isn't appropriate although both ECU and TCU in these cars are known to be reflashable. MY1999 USDM Diamante ECU & TCU are also reflashable however I don't know whether the TCU is integrated with the ECU in these cars or a separate unit.

Revisions:
18Oct2013 - female diagnostic connector required for harness
25Nov2013 - OpenPort 2.0 reflash uses a 2.5mm mono audio plug
22Oct2017 - Add H8 TCU info, manual ECU reflash pin (79) confirmed

Circuit diagram for an auto ECU harness (please let me know if you find an error!) - the blue outlines represent the connectors (I've lumped all the ECU connectors into 1):
bench_harness_auto.png
bench_harness_auto.png (12.22 KiB) Viewed 7028 times
ECU connector pin diagrams:
Magna_ECU_pins_s.png
Magna_ECU_pins_s.png (150.4 KiB) Viewed 6989 times
Last edited by WytWun on 22 Oct 2017, 22:48, edited 7 times in total.

z80
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Re: Making a bench harness

Post by z80 »

mate that is a great bit of info, thanks for posting it.
Twin turbo Mitsubishi 380GT -16 PSI boost with 3.9 litres and LSD conservatively at ... 270Kw @ 710Nm at the wheels!
Supercharged TMR380 ....complete with custom Quaife limited slip differential.........191kw @400NM at the wheels
No virtual dyno here.

WytWun
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Re: Making a bench harness

Post by WytWun »

I've edited the first post to make a correction: a female OBD2 connector is required (not male as originally posted) for the harness - the OpenPorts are a male OBD2 connector.

WytWun
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Re: Making a bench harness

Post by WytWun »

Added connector pin diagrams to the first post for reference.

BCX
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Re: Making a bench harness

Post by BCX »

Hey Andy,

few things to add:
  • Definitely need pin 1 of OBD. You mentioned you weren't sure, but this earthed to put the OBD bus into diagnostic/comms mode. Openport just earths this right before the 5 baud init.
  • CEL - when I wired my bench harness ages ago, the 12v side of the CEL is after the ignition switch. not a huge problem though, I found that it sometimes stays on even though the ECU is off. This could be my dodgy code though doing this also.
  • I've re-flashed my bench H8 ECU as low as 9volts no worries, the OP2.0 can still generate the voltage needed to reflash it sucessfully.
8th Gen Galant VR4
MK Triton [6G74 conversion]

WytWun
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Re: Making a bench harness

Post by WytWun »

BCX wrote:
  • Definitely need pin 1 of OBD. You mentioned you weren't sure, but this earthed to put the OBD bus into diagnostic/comms mode. Openport just earths this right before the 5 baud init.
Good to know, thanks!
BCX wrote:
  • CEL - when I wired my bench harness ages ago, the 12v side of the CEL is after the ignition switch. not a huge problem though, I found that it sometimes stays on even though the ECU is off. This could be my dodgy code though doing this also.
I don't really remember why I did it that way - it may possibly have been based on a schematic I'd found for an Evo bench harness - but rechecking the w/s manual schematics does indicate that the LED/lamp is tagged to the switched supply in the car loom. As a practical matter, it doesn't seem to cause any issue the way it is in my harness. I included it because it can be helpful in diagnosing a completely dead ECU.
BCX wrote:
  • I've re-flashed my bench H8 ECU as low as 9volts no worries, the OP2.0 can still generate the voltage needed to reflash it sucessfully.
So far I've not attempted to flash a H8 though I have an OP2 just in case... Given Tuffy's recent drama, I'm hoping not to need it for that purpose ;) But good to know that the risk may not be as severe as I may have implied.

BCX
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Re: Making a bench harness

Post by BCX »

BCX wrote:
  • I've re-flashed my bench H8 ECU as low as 9volts no worries, the OP2.0 can still generate the voltage needed to reflash it sucessfully.
So far I've not attempted to flash a H8 though I have an OP2 just in case... Given Tuffy's recent drama, I'm hoping not to need it for that purpose ;) But good to know that the risk may not be as severe as I may have implied.[/quote]

H8 is pretty resilient to reflashing. Even with low battery, the Openport still manages to generate the voltages needed. I definitely wouldn't recommend it though, at least try for 10-11volts at the minimum.

I've even pulled power mid-reflashing on my bench ECU. Have come to the conclusion - so long the block you're reflashing doesn't contain vector table and the routine at 0x10000, then you're all good. Otherwise it'll brick it, and processor will need to be desoldered and reflashed the old fasioned way. (I've salvaged a few locked vr4 ECUs this way)

What was tuffy's problem?
8th Gen Galant VR4
MK Triton [6G74 conversion]

WytWun
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Re: Making a bench harness

Post by WytWun »

I've been able to read the TCU ROM from both a TH 3.5 auto ECU and a MY2000 USDM Diamante ECU having finally identified the TCU reflash pin for these combined ECU/TCU H8 units; the first post has been updated with the pin info.

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[TUFFTR]
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Re: Making a bench harness

Post by [TUFFTR] »

Used your diagram to make the bench harness and successfully flash ECU's no issues.
Thanks man :)
Messy as shit though so I'll need to tidy it up one day.

WytWun
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Re: Making a bench harness

Post by WytWun »

[TUFFTR] wrote:Used your diagram to make the bench harness and successfully flash ECU's no issues.
Thanks man :)
Glad it worked for you!
[TUFFTR] wrote:Messy as shit though so I'll need to tidy it up one day.
Hehe... my auto harness is reasonably neat, but the manual one turned out like snarled fishing line :oops: :roll: . Gets the job done though :lol:

chaddy1974
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Re: Making a bench harness

Post by chaddy1974 »

Does anyone know what Pin 75 is on a manual TJ magna ?

WytWun
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Re: Making a bench harness

Post by WytWun »

chaddy1974 wrote:
16 Feb 2020, 17:14
Does anyone know what Pin 75 is on a manual TJ magna ?
It isn't used in the Magna application according to the schematics in the W/S manual, but checking other similar ECU connector pinouts (Evo 8 & Eclipse V6) suggests it would be used for the rear (i.e. after catalytic converter) oxygen sensor input signal in applications with pre & post cat O2 sensors. There should be a second set of pre & post cat O2 sensor input pins for Cali spec emissions applications (for the second bank in V6s) but I haven't found any references to the actual pin numbers that would be used for them :( (though I suspect they might be on 74 & 73 respectively).

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