17 replies to this topic

[DavidGraves]

Is anyone here familiar with reading a GM 1993 On Board Diagnostic plug in ?

 

Our long reliable K2500 Silverado has an intermittent miss and signals a code but I have not been able to read it.

 

Many thanks

 

Old truck....old owners.

 

David Graves

[pvstoy]

Most parts houses like pepboys, Kragen, autozone will read it for you free and even sell you the needed part. Walmart?

[DavidGraves]

Thanks Patrick

 

We live rural and the local parts house only has an OBDII device.

[Zoomad]

OBD 1 systems do not require a scan tool to read codes.   Use a paper clip and jump the terminals "a" and "b" together with the key on, engine off.  The check engine light will begin to blink.  Codes are two digits.  So for example code 12 would be one blink, pause and then two blinks.  

 

The data link will be under the dash on the driver side.  Here's a link to a site with a visual of the plug, terminal locations and a listing of the codes.  

 

GM OBD1

 

Read the codes and post them up.  I'll see what I can do to help.  I've been around a few of them...

[DavidGraves]

Many thanks

 

I knew about the paperclip jumper.

 

When I did that the dash light did not flash.

 

Mind you, truck was not missing then...just the Service Engine Soon Light came on.

 

I have printed the Code list

 

On the road today for a delivery....

 

More later.

 

DG

Edited by DavidGraves, 30 March 2021 - 01:33 PM.

[DavidGraves]

Howdy Zoomad

 

So far I have only been able to read a code 14.

 

I get one blink followed by two blinks and two blinks. ( is this code 14 or code 22 ? ? )

 

If I understand correctly I can only read one code...need to correct it and then any other fault code will appear.

 

Code 14 is coolant sensor.

 

I hope you are patient !   

 

DG

[Zoomad]

Alright, it's odd you got the single blink first.  If you took that and the next two blinks it would be code 12, which is the one to indicate there are no current codes.  I don't think that is the case here so bear with me.

 

Code 14 if that was it, is not specifically saying the temp sensor is the issue.  It's definition is that the coolant temp reached 275 degrees for 2 seconds.  Even as notoriously vague as the stock gauges are I'm going to guess the engine didn't overheat on you.  

 

Let's assume the first blink was just the light coming on for bulb check and then you got two blinks, pause and two blinks for code 22. That code is for the TPS (throttle position sensor) voltage being below 0.2v for 2 seconds with the engine running.  Now a TPS code could be a condition that could cause a rough idle and or poor or no transmission shifting. The issue could come down to a wiring issue, TPS adjustment, TPS not reading correctly or a possible PCM.  I wouldn't go buying a bunch of parts yet.  

 

Since the problem is intermittent, I'd wipe the code out by disconnecting the vehicle battery for 15 seconds and go back to driving it.  If the condition re-occurs and turns the light back on I'd recheck the codes and see if the same one came back or it was something else.  

[DavidGraves]

Thanks Sir

 

I will do a better job of reading the codes next time around.

 

Will it display more than one code if more than one fault exists?

 

David

[Zoomad]

Thanks Sir

 

I will do a better job of reading the codes next time around.

 

Will it display more than one code if more than one fault exists?

 

David

No problem.  

 

Yes, if there is more than one code set, it will display them all.  It will blink the first code, long pause and then the next code.  It will keep doing that until it hits the last code and it will start over with the first code and repeat.  

[DavidGraves]

Howdy Zoo

 

Got a better read of code.....

 

Code 32 only....

 

DG