1989 c3500 check engine light

barefootskier · 06-05-2005, 06:54 PM

my c3500 454 has a check engine light that comes on if driven about 5 miles at 65mph steadily. if i drive fast or aggressive the light doesnt come on, nor does it come on when in town driving, only at steady freeway speeds. first i need to check for codes, but i dont know how to get flash out codes or which terminals to connect to each other on the data link connector. please help. thanks for your assistance.

marble75 · 06-06-2005, 06:49 PM

i have an 89 2500 with a 5.7(350) and it does that but now im having worse problems i posted a message but no good replys yet if u figur it out plz let me know might be similar. thanks marble

marble75 · 06-10-2005, 07:10 AM

i figured it out on my truck... i talked to a few ppl and the think u have a M>A>P> sensor that is bad but mine was low fuel pressure...

mrjohnwayne · 06-19-2005, 12:14 PM

An easy way to pull the codes on the older chevy vehicles before the days of obd-II, (and i think 89 falls in that category but not sure) is you can take a paper clip and bridge the very top right pin and the very top 3rd from right pin on the computer connector located under or at the bottom of the dash on the driver side. The check engine light with flash with a code 12, stating that computer is operating normal then flash any codes that are in there through the check engine light itself. Ignitoin has to be on to work. It has been forever since ive done that so if anyone see's any errors in my statement please feel free to correct me. Hope that will help for future reference.

06-05-2005, 06:54 PM	#1
barefootskier Junior Member Join Date: Jun 2005 Posts: 5	1989 c3500 check engine light my c3500 454 has a check engine light that comes on if driven about 5 miles at 65mph steadily. if i drive fast or aggressive the light doesnt come on, nor does it come on when in town driving, only at steady freeway speeds. first i need to check for codes, but i dont know how to get flash out codes or which terminals to connect to each other on the data link connector. please help. thanks for your assistance.

06-19-2005, 12:14 PM	#4
mrjohnwayne Moderator Join Date: Apr 2005 Location: Texas Posts: 3,220	An easy way to pull the codes on the older chevy vehicles before the days of obd-II, (and i think 89 falls in that category but not sure) is you can take a paper clip and bridge the very top right pin and the very top 3rd from right pin on the computer connector located under or at the bottom of the dash on the driver side. The check engine light with flash with a code 12, stating that computer is operating normal then flash any codes that are in there through the check engine light itself. Ignitoin has to be on to work. It has been forever since ive done that so if anyone see's any errors in my statement please feel free to correct me. Hope that will help for future reference. __________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4

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06-06-2005, 06:49 PM	#2
marble75 Junior Member Join Date: Jun 2005 Posts: 6	i have an 89 2500 with a 5.7(350) and it does that but now im having worse problems i posted a message but no good replys yet if u figur it out plz let me know might be similar. thanks marble

06-10-2005, 07:10 AM	#3
marble75 Junior Member Join Date: Jun 2005 Posts: 6	i figured it out on my truck... i talked to a few ppl and the think u have a M>A>P> sensor that is bad but mine was low fuel pressure...