Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing GDI Gauges Intermittent Fault

Thanks Roger,

I have added the splice and connector to the list of things to check/wiggle while monitoring the OHMs.

New Multimeter probes arriving today.

BTW, how best to fix a splice? should it be soldered or would a block type connector be ok? My soldering skills are poor to fair (my tools must be to blame) and I don't fancy going near all the wiring in the fuse box with anything hot.

Regards

If as you say the OBD also fails when the gauges fail, that might imply the fault is further back towards the ECU, or perhaps even at the splice joint. From the splice there appears to be separate signal wires running in parallel to the OBD and VDO.

Re soldering. That would be the best solution in principle but maybe tricky getting access, depending on the location. If it has to be soldered and things look fairly clean when the insulation is off may be try and solder the complete splice rather than the wires individually. Apply some flux first. You might need a substantial iron to get enough heat in too.

Hi Mark

You might find it easier to do the wiggle/ohms check as follows:

The CAN BUS High and Low should be wired to pins 14 and 6 of the diagnostic socket.
If you get a pre-wired diagnostic plug, something similar to one in the link, you could connect your meter to the wires that are connected to 14 and 6 of the plug with croc clips, make sure none of the wires from the plug are shorted. Plug this into the diagnostic socket, make sure the ignition is off, keys out and check the zero volts on the multimeter. Then switch the meter to ohms, it should show your 66 ohms and that leaves both hands free to wiggle all the CAN BUS connections.

https://www.amazon.co.uk/CERRXIAN-C...2281435176698&psc=1&gad_source=1

Regards Tony

When I needed to add an extra feed to the reverse light bombtail I twisted a good bared length around the outside of the hollow crimp MMC use then soldered in place using my larger 80 watt iron. I flooded the crimp with solder as well then finished job with a couple of layers of heat shrink.

I imagine most bombtails (splices) use the same crimp tubes with bared cable ends poked through (maybe twisted together) then crushed by flattening one end of tube.

Mark, I can confirm that VSS signal on brown/white wires shared via bombtail feeds VDO gauge directly on pin 19 as well as pin 86 on ECU. This would explain why speed display remains when OBD readout fails.

Mark

Me again forgot to mention when doing wiggle test don't forget the connectors into the ECU and BCU

Regards Tony

Hi,

Got to grips with a few things today.

Cleaned the contacts on the Chassis/Engine connector.

Found the splices, pic below, but they look pretty good so decided not to cut the heat shrink off (for now), your opinions welcome.



I did manage to wiggle all the parts of the loom and connectors identified while monitoring on the multimeter but could not get any reaction.

I disconnected the SAT-BUS from the Rev counter which effectively also disconnects the fuel and water temp dials, but will have to get some trips in to see what happens.

Regards

Well done locating those splices! On the face of it they look like the regular barrel crimps.

Perhaps worth doing a light pull test on those UR and SR wires just to check the crimping integrity. That would at least rule out a poor mechanical crimp but unfortunately would not necessarily rule out high resistance from any corrosion.

Have you considered re crimping through the heat shrink? Perhaps give them another squeeze (in the orig direction) with a crimp tool. Then just sit back and see if the prob goes away.

PS- Where were they located, other GDI owners may be interested?

Worth mentioning that since the introduction of the schematic style wiring diagrams round about 2006 the loom distances are quoted in mm between each split, bombtail, termination etc. It's relatively easy therefore to measure from an adjacent feature to find what your looking for.

An example is in Rog's post here. The CAN low bombtail is 75mm from the chassis to engine loom connector C48, CAN high a further 60mm.

Sorry for the thread drift, but what's a bombtail, Richard? Google came up with nothing.

TBH I'm quite glad my old crate has got good old traditional brass bullets in nearly all of its wiring

Hi,

I had realised, as Richard points out, that the connector and splices must be close together with the Relays shown in the diagram. So in the Fuse Box, just moved the BCU out of the way (just Velcro in) and removed a bit of tape.

Good idea re pulling on the wires and re-crimping, can't hurt to try.

Thanks