Check engine light

[dlivewyer]

My check engine light is on constant. When I try to read the codes, it will not go into diagnostic mode. When I turn the key on, the check engine light just comes on and stays on. I disconnected the battery and cleared the codes and retried to read codes and it did the diagnostic mode flashes and that's it. When I started the motor, check engine light came back on. I tried to read codes and it did the same thing, no diagnostic mode, just steady on. It's a '94 5.7. Any insight would be appreciated. Thanks.

 

[PlayingWithTBI]

When you say "read codes" do you mean by using the paperclip trick? If so, are you reading the codes with KOEO (Key On Engine Off)? When you turn the KOEO does the SES light flash once, then goes on steady?

 

[dlivewyer]

When you say "read codes" do you mean by using the paperclip trick? If so, are you reading the codes with KOEO (Key On Engine Off)? When you turn the KOEO does the SES light flash once, then goes on steady?

No paperclip, I have the "code reader" that only has 2 pins that essentially does what the paperclip does. When I turn on the key KOEO, the light does not flash, just comes on and stays on.

 

[Erin]

No paperclip, I have the "code reader" that only has 2 pins that essentially does what the paperclip does. When I turn on the key KOEO, the light does not flash, just comes on and stays on.

When my uncle hooked his scanner to my truck, he had to get power from the battery. Don’t know if that’s your issue.

 

[dlivewyer]

When my uncle hooked his scanner to my truck, he had to get power from the battery. Don’t know if that’s your issue.

When I disconnected the battery to clear codes and hooked it back up, I plugged in my "scanner" and the CEL flashed like t is suppose to.

 

[dlivewyer]

OK I got the code reading issue fixed. It shows a code 43 (master relay open or grounded) Where to look or what to check?

 

[PlayingWithTBI]

It shows a code 43 (master relay open or grounded) Where to look or what to check?

Where did you find that description? This shows different definitions.

GM OBD I Trouble Code Chart

Code Description Code 12 No distributor reference pulse (diagnostic test active) Code 13 Oxygen sensor circuit open or no

repairpal.com

The best thing to do is get a real scanner and look at the data stream. Codes help but, data tells you more

 

[dlivewyer]

Where did you find that description? This shows different definitions.

GM OBD I Trouble Code Chart

Code Description Code 12 No distributor reference pulse (diagnostic test active) Code 13 Oxygen sensor circuit open or no

repairpal.com

The best thing to do is get a real scanner and look at the data stream. Codes help but, data tells you more

I got that description from the book that came with the "scanner". It flashes blink, pause, blink-blink, 3 times in a row, which should be code 12(confirming it's in diagnostic mode). Then it pauses and flashes blink-blink-blink-blink, pause, blink-blink-blink, 3 times in a row, which should be aa code 43. My book says that it's a master relay open or grounded. Your link shows a code 43 as a knock sensor error. Where can I get a "real scanner"?

 

[Schurkey]

Where can I get a "real scanner"?

I've bought mine "used" on eBay.

When it's my money, I buy used, professional-grade scan tools in preference to "new" consumer-grade tools.

Most recent purchase was a Snap-On Solus Pro; about 1/10 of "new" price. $350 delivered to my door.