1992 740 DTC Code 1-2-3

Post by **Enginer** » 19 Mar 2015, 05:51

Just swapped for a later (940) B-230 Turbo, using original ECU, MAF, O2, etc. Engine refuses to get out of Limp Home Mode. DTC code 1-2-3 which one source says is ECT, engine coolant temperature. A post on another site said that he could'nt clear the code, even tho the car was running fine.

Can a ECT malfunction cause limp home? This engine was running, with the ETC, in an 1987 760, and I did not change it after the swap. Is the 1986 ECT not compatible with a 1992 ECU?

Thanks in advance!

93Regina · Post by **93Regina** » 19 Mar 2015, 11:26

Enginer wrote:...Is the 1986 ECT not compatible with a 1992 ECU?

Here's the electrical difference:

lummert · Post by **lummert** » 19 Mar 2015, 15:04

No, it's not compatible. Use the original 940 (or replacement) ECT.

93Regina · Post by **93Regina** » 19 Mar 2015, 19:07

Enginer wrote:Engine refuses to get out of Limp Home Mode.

LH 2.4 - Emergency Program: There is a "limp home" function provided if the signal from the air mass meter ceases for some reason, such as the hot wire burning off. A pre-programmed value is used for injection duration, allowing the vehicle to be driven slowly to the garage.

Post by **Enginer** » 20 Mar 2015, 12:13

turned out to be the incompatible ECT sensor. The swaped motor sensor was blackened, so it looked exactly the same as the LH2.4 black sensors. Thanks, all!
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The 92 engine had one pin in the Engine Temperature sensor, the 86 had two pins in the connector. Any ideas? Nothing in the 4 manuals I have...

lummert · Post by **lummert** » 20 Mar 2015, 12:26

I've seen generic replacment ECT sensors for LH2.2 with black instead of blue connector.

93Regina · Post by **93Regina** » 20 Mar 2015, 21:51

Enginer wrote:92 engine had one pin in the Engine Temperature sensor, the 86 had two pins in the connector....

Both ECTs-Engine coolant temperature sensor-have two pins, as shown in photos above.

First ECT shown shows a resistor in series, whereas in second photo, separate resistors going to ground.

Post by **Enginer** » 21 Mar 2015, 18:11

Opps. We go astray. The engine temperature sensor, located to the left of the ECT, is under intake runner 2. One of my B230 blocks has two pins and one has one pin. One of the manuals says one pin is for the gauge cluster, the other something else. I looking for a wiring diagram for the two pin version because the connector failed and I do not know if It is important which connector goes to which pin.

lummert · Post by **lummert** » 21 Mar 2015, 18:21

http://www.volvowiringdiagrams.com