Unknown problems with 1998 GMC suburban 5.7

[Matt Harshaw]

I just purchased a 1998 GMC Suburban 2wd 5.7L

I need to get it to pass emissions for the Tag. I was an emissions inspector for 8 years and have about a decade of service under my belt. Here is what I've come across.

Check engine light was on for P0452 when I bought the car. No problem. I dropped the tank, found the wires to the tank sensor were rubbed through. Easy fix. (Done 1 week ago)

The only other problem was a slight bogging when getting on the gas from a dead stop while in drive. (intermittent)

Found an air leak on the intake at the fuel spider plug o-ring. (sigh) so I pulled the intake off replace the gaskets (the suspected o-ring was in pieces). (yesterday)

The big problem, though, is the monitors will not set. after the initial replacing of the fuel tank sensor, I drove through the GM drive cycle multiple times. No MIL came on, no codes, etc. The only monitors that set were the initial 3 (comp, misfire, fuel). Even after 20 full cool down and starts and 200+ miles, no other monitors would set. This was before the intake gasket replacement. and is still an issue

After the intake gasket replacement, I got a code for the coolant temp sensor (P0118). Yet it has not tripped the light, even though the code is not pending. (not too worried about this, as the wires are old and should be an easy fix, but thought it may be pertinent to the computer issue)

Then for just a moment this afternoon I had a P0020 at start up but it went away when started up.

Any advice or insight would help.

[barry G]

wires rubbed, interacted with computer to get a code.

 

You could go to ebay and grab another computer for less than 100.

there is one that takes your VIN, licensed by gm to program a good used one...

89 bucks or something.

 

I have a manual tranny truck, no DRL..the fuse box on the left of the dash is minimal.

the ecm still gets warmed...

That is when I found ways to get a new ECM option in my favorites. Do not need one yet..but I do think of the automatics in the same years.

 

right now, I have one erro with no cure, it passes inspection anyway..code 420. catalyst below threshold.

manual tranny problem. I can lug to idle in high gears..triggers cat code.

[Jay P]

Do you have something to read live data with? You said you had a temp sensor code. If the computer doesn't think the engine is up to temp it won't complete the drive cycle stuff. You need to know what the computer is getting for data.

 

Jay

[Jsdirt]

The guy who designed the GM drive cycle needs to be punched in the face ...