I've been having some cold start idling issues recently so yesterday evening I checked the codes and got 3-1-1 and then 2-3-2, so I reset them. The next morning I drove to work and checked again and got 1-2-2, 2-3-2, 3-1-1. Another thing to note is that the check engine light came on AFTER resetting the fault codes.

These codes were all taken out of socket A2. I also have a B2 which I thought didn't exist on a 740. Can anyone elaborate on 1-2-2? I've read that it can be an air temp sensor or 'speed below limit' or something like that. I'm more concerned about which one could be causing the CEL. My speedometer intermittently works so 3-1-1 makes sense. Any tips are greatly appreciated! Oh and I have a LH2.4 Regina Ignition.

Thank you!

 

LH2.4 and regina are mutually exclusive. LH2.4 is the bosch fuel injection used on most 240/740/940 between 1989 and 1995, while Regina/Rex is an alternate system used on some models.

 

Oh okay. Well my system is Regina, not Bosch LH2.4 then. It has the larger square ignition module on the driver side of the engine compartment. So, are the codes the same for both systems? And what is this 1-2-2 code?
Thanks.

 

find hte regina codes near the bottom of https://www.volvoclub.org.uk/faq/Eng...agnosticCodesi

says your temp sensor or its wiring is funky.

 

I'd start by changing that Air Temp. Sensor although the OBD system is not all that reliable but you gotta start somewhere, right?

 

I might check the temp sensor via unplugging the reginal ECU and measuring the resistance at the temp sensor pin. if its open circuit, I'd unplug the temp sensor, ground the wire, and measure that resistance again. if its shorted to ground, unplug it and don't ground it and measure it. if those last two checks pass but the resistance is off for the temperature range, THEN I'd replace the sensor, but if either of those last two tests are off, then its a wiring problem

 

Gotcha Pierce, I will test it this weekend and see what is going on with it. Thanks for the input so far everyone. I hope everyone is having a great Thanksgiving!

 

UPDATE:

Alright well it has been awhile but I finally got around to working on the volvo. So I went ahead and purchased a new IAT Sensor because they were on sale at IPD during Thanksgiving. After replacing, there was no change and I was still getting codes 1-2-2, 2-3-2, & 3-1-1. Today I cleaned my throttle body, replaced the throttle body gasket, the flame trap and checked vacuum hoses for holes/cracks (I was not able to find any).

Now on to the electrical problem. I've attached pictures of the connectors and the wiring diagram from my chilton manual. Here are the continuity tests I ran with the IAT sensor unplugged:

IAT connector ground to ground on intake manifold: continuity
IAT connector signal to IAT signal at the MAP (green 3-pin connector): no-continuity
IAT connector ground to IAT signal at MAP connector: continuity
MAP connector pins: no-continuity between any pins
IAT connector: no continuity between pins

After this I plugged everything back up and then disconnected the battery and checked continuity between pin 10 and 6 on the ECU and got no-continuity.

Hopefully I didn't confuse anybody. If there was a flaw in any of these tests please point me in the right direction or to any additional tests. But from these, it is looking like there is a break somewhere in the wire from the IAT to the connector at the MAP and it is shorting to ground. Does this sound correct?