I have a land rover defender td5 2004, I changed the ECU, now I have a problem with the temp gauge, it reads that is at middle temperature when is cold, and it reads cold when should be at the middle. What should I do?

 

Did you use the same year ECU?
It has to be a ECU program problem.

 

There is also a variation on ECU for petrol vs diesel; the heat signal to the gauge comes out on different pins. One work around might be to use a scanner or Ultra Gauge ($70 US) to read the live OBDII data for coolant temp. Schematic from RAVE attached.

 

It is a diesel engiene. I bought the ECU, was supposed to be the same year and for a diesel engiene.

 

Also may want to check the wiring to the sensor, the gauge will act strange if sensor wire broken or grounded (pinched wire harness). The diesel and the petrol suffer the same design limit, in that "old school" Rovers used a separate sensor to move the gauge, newer ones use a single sensor, the ECU reads it, the ECU uses that data for various purposes, and the ECU sends a modulated signal to keep the gauge at center position most of the time when warmed up. Instead of creeping up every week as conditions change in the cooling system, the ECU waits until you are almost fried and then pops up the gauge. A scanner will tell you what temp is at a cold start, which shold be close to ambient in your parking area. If I unplug my sensor, the ECU reads it as -40F, and that is what is shown on the OBDII port. I guess you could also have a bad temp sensor.

The specs for the sensor used with the Bosch ECU are:

 

My defender is 2004 td5, I bought a used ECU but I do not know nothing about it . I was thinking in buying another temperature gauge, but what type do I have to buy?

 

I have a 2004 td5 defender, I just change the ECU, after that the temperature gauge is working backwards, when the engine is cold the gauge is at the middle, when the engine is hot the gauge marks it is cold. I went to land rover Guatemala and they could not fix the problem, now I am thinking to buy another gauge temperature but do not know what to buy.

 

Can you post a pic of the temp gauge?
We have almost no Defenders here in the US.
And no '04 Defenders for sure.

 

Here's diagram for a 2002 Defender, there is a slight difference in wiring on a TDI vs a TD5.

 

I talked to the person who sold me the ECU to find out from what year was the ECU, It is from a 2,000 Defender, and my defender is 2004