Check engine light flashing dim while driving

[Supervillainmc]

This morning I started truck and drove . After a little while my check engine light started flashing very dim continuously. Even when I shut it off and turned they key. The truck drives and idles fine. Any suggestions? Thx again

 

[Wes Harden]

Sounds like either the lamp circuit has an intermittent short to ground, or the test circuit at aldl has an short to ground.

 

[Supervillainmc]

Sounds like either the lamp circuit has an intermittent short to ground, or the test circuit at aldl has an short to ground.

Thank U. I checked the codes. I’m getting a code 51. I think the computer might be bad. I have an extra. Gonna swap it in morning and see if anything changes

 

[rampage]

Everyone is always so quick to blame the computer.

 

[nvrenuf]

Seems like I’ve read that (among other things) the charging circuit uses that light as a load on the circuit to excite the alternator to charge. I’d check the alternator.

 

[dyeager535]

Seems like I’ve read that (among other things) the charging circuit uses that light as a load on the circuit to excite the alternator to charge. I’d check the alternator.

AFAIK any alternator tie-in is done with the "Charge" indicator. I don't know what was done 87-89, but in 90-91 the clock position has a charge indicator light. But even that didn't seem consistent, perhaps it depended on the alternator being used.

Disconnecting and reconnecting the ECM wouldn't hurt either. I've had pins on the ECM connector lose their locking function, and cause some weird intermittent codes. Frustrating to figure out.

 

[nvrenuf]

That makes sense Dorian as mine is a ‘91.

 

[diesel4me]

????.....

 

[dyeager535]

I saw your post somehow ended up in the Cybertruck thread.

Do you have any engine modifications? Aftermarket (I'm talking the off the shelf one size fits all type, not ones custom burned for your modifications like Howell does) chips are undeniably, absolutely, snake oil (arguably harmful to boot) so if you have no modifications, stick with the stock PROM.

 

[Supervillainmc]

I saw your post somehow ended up in the Cybertruck thread.

Do you have any engine modifications? Aftermarket (I'm talking the off the shelf one size fits all type, not ones custom burned for your modifications like Howell does) chips are undeniably, absolutely, snake oil (arguably harmful to boot) so if you have no modifications, stick with the stock PROM.

Only Mods I have are Hooker long headers,Flowmaster 40s, 9c1 Injectors,Adjustable Regulator. Stage 3 Tow package with shift kit and Corvette Servo, Stock 4 Bolt Main , 410 Gears

 

[dyeager535]

Headers, different injectors, and changed fuel pressure require a new, properly tuned chip to run right. I'd get with Howell. Tbichips.com seemed to have gone downhill enough to be avoided unfortunately.

 

[Supervillainmc]

Headers, different injectors, and changed fuel pressure require a new, properly tuned chip to run right. I'd get with Howell. Tbichips.com seemed to have gone hill enough to be avoided unfortunately.

Thank U. I’m gonna do that