Some more DTCs

[matuva]

At the beginning of the week, my Blazer started being a bit more longer to start. Then I noticed engine was less "clancky", then cruise control quit working, and finally she stalls while gently cruising on the motorway. No SES light.

Yesterday evening, I put a new Flight system PMD + new extension to replace the grey Stanadyne PMD (6 months old) at the same place (relocated behind the grill)

My Blazer starts and runs fine.

This morning, on the way to work, I noticed that cruise control again quit working :skep:

At noon, back home for lunch, SES light came ON. She comes OFF as long as my speed is under 80 kph and or I stop accelerating. As soon as I touch accelerator and rpms go over 1200~1300 and or speed goes beyond 80 kph, SES stays ON.

At home, I hooked my scanner, and here are the codes I read :


I cleared all codes, went for a drive. 10 kilometers later, still having this jerky SES light coming On & Off...
I parked the Blazer, didn't shut off, and with engine idling, I got this:


So; DTC 41 let me know I have no more brake light. I will fix that.

DTC 35? PMD, resistor and extension are brand new, IP is a reman less than 20k kilometers, I always put 2 stroke oil in each tank ...

DTC 38? what's this switch? Where is it located?

DTC 84 and 99? Should I change the accelerator pedal?

What's your opinion on these codes?

This "idiot light" is turning me mad :mad2:

 

[NVW]

The brake and accelerator are part of the cruise system, I would go through the grounds before anything else.

 

[Will L.]

Brake switch on the pedal. Test by someone watching brake lights while you hold brake pedal down, then with a finger operate the switch on/off/on multiple times. This could explain 38 & 41. Factoring in all the other codes, grounds or maybe the harness side of the connector where your extension cable plugs in is more likely.

 

[WarWagon]

DTC 84 and 99? Should I change the accelerator pedal? No. Run the pedal through a couple sweeps while watching the voltage on all 3 pots. Then floor it and let it snap back to idle, engine off. See if the WOT and idle voltages are the same each time. Ignore code 99 by itself.
The APP has it's own wire run from the computer with a connector about 6" from the computer, ECM, plugs.

Any shorts on the 5v line or bad grounds, including power like corroded fuses, bad ign switch, batt cables, bad diodes in alternator... can all cause the 5v line to weird out. So if you have a sensor shorting out you get all kinds of failures off the 5v reference.

I find that cycling the key too soon before the computer shuts off can trigger a code 99. Like when you don't get a SES light after quickly off-on cycle of the key. Watch the voltage readings while moving the APP after turning off the key. You will see how long the ECM stays active after key off.

After all this if you still have 2 APP codes you are looking at needing to replace the APP. :suicide:

 

[matuva]

OK, thanks guys.

I know what to do saturday morning

 

[vegtech]

you need a brake switch

 

[matuva]

I put a brand new brake switch this morning.

Brake lights are OK now, DTCs 41, 84 and 99 are gone, but I'm still having the idiot light ON as soon as I accelerate.

DTCs 35 and 38 are still there.

I put a new brand new in the box PMD, #9 resistor and new extension just before DTC 35 appears. It was to replace a grey stanadyne after I experienced stalls.
PMD is a flight system from Pensacola.

Should that explain DTC 35?
How comes DTC 38 remains? The brake switch is brand new now...

 

[matuva]

Swap to my buddy's PMD : no more idiot light, DTC 35 gone.
Put back mine, MIL ON again and DTC 35 again:skep:

We changed the brake switch, brake light work fine... and this evening, again no more brake light:mad2:

Anybody gets the wiring diagram of a 1994 Blazer, especially brake light circuit?