Hello Volvo friends, I am having an issue retrieving trouble codes
on my 1991 240 wagon, the check engine light came on about a week ago
and I've tried the onboard diagnostic center under the hood and dont get any
codes after putting the plug in either 6 or 2
is there a way to plug in an OB2 scanner? the good news is the car seems to be runnig ok, thanks for any tips! AMS

To answer your specific question, the type of OBD reader you're probably thinking of are OBD-II readers that can only be used with the OBD-II diagnostic connector ports located in the interior of later 1990's cars (1996-on), not the underhood OBD (OBD-I) diagnostic connector in your car. Even if they could be used, your diagnostic connector port would need to be functional. As others mention, you perhaps need to be a bit more precise describing not being able to get any codes.

The code retrieval and reset procedure as well as other diagnostic procedures you are able to perform at the connector are described here in the brickboard FAQ
Engine: OBD Codes (700-900 FAQ)

If the red LED won't light at all when you depress the button with the ignition switched on (KP-II) and the pigtail in either socket 2 (fuel side) or 6 (ignition side) then you have a basic electrical problem likely at the diagnostic socket.

If it glows faintly without having to depress the button (possibly only noticed in the dark) then there may be a ground problem on the ECU circuit board. This was more common with a few of the early LH 2.4 ECUs that also had failing fuel pump control, not the later ones like yours. With a bad ECU causing the LED to glow, the OBD socket was generally still capable of being used.

For further information, you may want to check out this older thread over on Turbobricks, possibly the same problem as yours
Volvo 240 OBD not working (Turbobricks)
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

What fouled me up a time or 2 is that the button needs to be held down for more than 1 but less than 3 seconds. I finally used the timer on my phone rather than counting. Then release the button and wait a few more seconds for the flashing to start.
--
1991 240 Sedan auto

Hi,

You say you don’t get codes?
Are you getting any blinking red light from the little box?
I ask as there might be corrosion someplace.

The CEL and the Service light are two separate animals.
The CEL is for emissions purposes and the Services is an oil change reminder.
I think it might trip on every 7,500 miles but I’m not sure. It is resettable from a peg on the face of the instrument cluster’s bottom right hand corner.

As I remember the # 6 socket is a test socket to operate various components a visual or hearing test. I haven’t had to mess with my diagnostic port in a long time.

If the EGR doesn’t respond with a temperature change, in the down pipe or body, after a set time, the ECU trips the light on!
The car runs fine, it’s the eyeballs that get strained and then, the brains! (:-)

I have had this EGR code twice on my 1991 and each time it’s been the controller valve to the EGR getting a plugged up exhaust or intake equalization vent under its little gray cap!
Originally it had a foam rubber that rotted. I replace it with a polyester fabric stuffing piece.
This is located on the left side strut tower.

I hope some more BB subscribers chime in as I’m not that keen about what causes no codes.

Phil

There are two ways to interpret "don't get any codes." The good way is to mean he gets 111 from each test, fuel and ignition. The code for all is well. The bad way is to mean there's no response at all. That would take some troubleshooting, especially if the engine is running well.

"Middle age is when a narrow waist and a broad mind begin to change places." -E. Joseph Cossman

(no I'm not bhouston -- something amiss with the logins here)

I emailed Jarrod about the reply to a message, log out, and remain logged in under the user of the message you replied to or something.

OBD-2 (II) is 1996 and later on US gasoline car with oxygen sensor before and downstream of the cat and uses a DB-25 connector so you can connect the code scanner.

The procedure from the Volvo 700/900 series FAQ. Copy and paste URL to new browser tab or window for your engine control systems.

https://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm