ECU replacement Issues

[Drakman]

Hi Guys and Girls,

 

I am having a Haltech Elite 1500 programmable ECU fitted to my 2014 Duratech Roadsport 175 Caterham to replace the locked Lotus ECU.

The business doing the install tell me they have to "piggyback" the original lotus ECU to make it read the instruments but they can't get the water temp gauge to work.  Their answer is to replace the Caterham temp gauge with a Haltech digital temp/AFR gauge.  Now I can wear this so far, I would prefer not to have the piggyback thing and I would like to keep all the original gauges but it is what it is.

Now they tell me that the original locked, piggy backed, Lotus ECU is running the instruments and it can't find the engine sensors because the Haltech unit is now doing that which means the engine check light is on all the time.  Surely this can't be an acceptable thing, is there an answer to this issue?

Has anyone here had any experience with this sort of thing. 

 

Cheers
Dave

[MV8]

The explanation makes sense except that it isn't "piggybacking" to use the old ecu just for the gauges. The haltech is standalone. I would just disable the check engine light or switch to a standalone temp gauge. The check engine light doesn't mean anything coming from an ecu that isn't running anything but the gauges.

"piggybacking" would be an add-on that manipulates the original ecu in some way for tuning or whatever.

 

Edited December 22, 2022 by MV8

[Drakman]

Hi Again MV8 and thank you for the explanation. 

 

So the check engine light can be disabled then.

 

If the piggyback thing is just for the gauges could i replace all the gauges with ones that will work with the Haltech and completely remove the old Lotus ECU?  I take it that if I could remove the old ECU the Haltech would then operate the check engine light and the check engine light would work as normal?

 

This is all new territory to me.

 

Dave

 

[MV8]

Possibly. The haltech has a few programmable digital outputs (DPOs) that can be setup to have the check engine light come on for a period of time at start up and/or key on-not running, but the particulars or if it would actually come on to warn you about an internal error would be in the programming manual which I have not seen. I also don't know your schematics as those are not freely available on newer machines from CAT.

There is no need to remove the original ecu. Disabling the check engine light can be as simple as removing the bulb.

I don't know what instruments you have. Traditionally ecus have their own dedicated sensors and the gauges have their own sensors. The instrument determines if you need a separate sensor for the gauge. I'm sure haltech has a temp gauge that can be driven by the haltech ecu based on the haltech temp sensor. Do you have separate individual instruments or a single module cluster that contain multiple instruments? Some pics of your car dash and engine bay might help. I'm in the dark.

I think I would leave the cat ecu installed, remove the check engine bulb, and maybe use DPOs to control the cooling fan relay(s) on (10 deg above thermostat open temp) and off (5-10 deg below on) temps and speeds, add an over temp and low oil pressure warning light/buzzer, and perhaps a shift light.