Is anyone aware of a breakout box and harness adapter that will accommodate the 35 pin ECU connector in the XJS. I have an 89 with Marelli. After quite a search, I found a unit for Harleys that use Marelli EFI. The harness and box combo sells for about $450 (ouch). Part numbers are MS531-4015 and MS521-3037 respectively, but I'm not sure it would even work with our cars. Anyone know of anything else?

 

I have an 89 xjs parts car... can you send a photo of what you want and where it is located...
ken in wv

 

What are you trying to achieve? a BOB is a diagnostic tool.

 

A BOB is used diagnostically to determine whether the ECU is in fact receiving a particular signal from various sensors (i.e., crankshaft, coolant, etc). If the sensor tests fine, but the problem persists, is the signal actually received and processed by the ECU? Is the problem due to frayed, baked or open wiring? A BOB is a much safer and more efficient way of determining this, rather than probing the delicate wiring at the ECU connector. So, can anyone recommend a BOB that will work with our 35 pin ECU setup?

 

Good to know you have a parts car, and thanks, but I'm talking about a common Dx tool.

 

Its not difficult to make this BOB, all you need is:-

An appropriate case.
LEDS
Resistors
Wire
Banana plugs
ECU connectors, off old ECU

Then each signal would have an LED and appropriate current limiting resistor between signal wire and ground. This will work for pulsed and on/off signals. Not too well for coolant temperature or any other variable voltage sensor. What would work for this are banana plugs you could use to attach a DMM.

 

Thanks for the thought Warren. If the fabricated box were to interface like a BOB does, it seems I would need to correctly wire all 35 pins to leds so that the signal could be checked when the car is running. Or alternatively the 35 pins wired across the box to the connectors, with leds and banana plugs to connect a DMM or scope for just the critical inputs. Is that correct?

 

A BOB is ALWAYS in parallel with the signal, unless it needs to measure current.

Commercial BOB's that have an input and output connector so they interface in series with the UUT (unit under test) are still actually in parallel.

I don't use a BOB I use a cut paper clip and insert it in the connector but I have been doing this for 35 years, you do need to be careful not to short any pins.

If you made a BOB you would only need to wire the signal input and output pins as needed.

I would put LEDs across all pulsing input/outputs, like injector drivers tach input

I would wire banana plugs to variable sensors like all Temp sensors.

 

Thanks again Warren, your insights are much appreciated.