Getting DTC 48 and 64 (I still need to replace the passenger header gasket)

tested the harness with KOEO and I am getting 12.30 volts between pink and ground wire.

car will run fine in open loop, then when it goes into closed loop run horrible, but no SES. It will run ****ty for extended amounts of time then sometimes the SES will come on and run better but not perfect. MAF is a ACDELCO unit with about 15k on it.

I did an intake oil leak fix and an aluminum elbow and this issue appeared soon after...yes, all the intake bolts are torqued correctly. no vacuum leaks, unless they are tiny because in open loop the car idles normal.

 

When you are testing the pink wire for voltage, did you jiggle the harness to see if there is an intermittent break in the wire? Did you check the pins on the MAF and in the harness connector for damage? Did you try hitting the MAF with a screw driver to see if it induces the erratic engine behaviour?

When the SES light comes on, are both the codes always there?

Do you have the ability to scan the PCM and read the O2 sensor voltage (both sides) and the long term fuel corrections for both sides?

 

You probably didn't touch the maf when you did the install (I didn't). Try putting back on the original elbow and see if it clears up?

Maybe there's someone you can bump into that will let you swap their maf to test? Otherwise car-parts.com has some good prices on used stuff(go to the lowest number on the list that has a price). I think it's called an Air Flow Meter and lowest was under $15.

Hal

 

well test MAF resulted in no change.

will inspect harness again for damage, runs great til closed loop, then stumbles and spits and hesistates, push in the clutch and rev...seems okay. Try to accelerate with load and runs like poo poo.

 

did you try putting the old elbow back on? Maybe elbow's iat connection came off or the connection to the tb is off on the bottom.

Hal

 

old elbow was torn and damaged, no around anymore. I will check under the TB for bad seals.

just inspected the harness for the MAF seems okay, checked the PCM side also.

replaced the injector O-rings for good measure.

weird that this happened after my intake oil leak fix...damn.

 

White Knight is having a problem with this exact same code here: https://www.camaroz28.com/forums/sho...ht=maf+voltage

Hal

 

Problem is you have an ODBI system and I have ODB2. My shop manual lists P0100 through P0103 error codes for the MAF. Shame you can't hook a ODB2 pcm up to it and get info from that (I can swap to OBD1 so no reason why you can't do the opposite but you'd need a different plug and reader). Get a shop manual off ebay, they are cheap now, and it would definetly help find the problem.

But, the main things the manual pointed out for possible problems were, MAF, power issues, PCM, MAP sensor (I know it has different codes but problems with it also throw MAF codes) and intake vaccum leaks.

Hal

 

OBD-II uses flow rationality tests to determine if the MAF reading is "in the ball park". That means is would use MAP in the speed-desnity calculation to compare the calculated flow to the MAF measured flow. That sets P0101. OBD-I doesn't have that diagnostic. DTC 48 is simply for the electrical circuit.... its either complete or it isn't. So a faulty MAP isn't going to cause an MAF code in OBD-I.

 

Oh, good to know. Whelp, then also make sure the MAF grounded correctly with zero ohms to ground.

I had a REALLY weird problem with a ground to my ABS/TCS. I had installed an in-line fuel pump and had to move my traction controll ABS unit for the blower. So when I got it all back together my ABS and TCS wouldn't work. Really thought I had just messed up my brakes in some way. Even a shop couldn't figure it out. Whelp, after years I finally decided I was going to find that problem. I found that the ABS ground was high ohms. Weird, it was wired straight to the frame along with the fuel pump ground (ran both the power and ground for the pump from the front strut pillar because both power and ground blocks are right there). I finally just disconnected the fuel pump and bam! The ABS/TCS worked again! Weird, but the stupid fuel pump was sticking the ohms high even after turning the car off for 2o minutes. I then moved the fuel pump to it's own ground and everything is fine now. So yes, even check the MAFs ground for zero ohms.

Hal

 

is it possible for the one header gasket to be bad enough to cause this problem?

I replaced the drivers side gasket and now I think the passenger side needs it badly.

 

replaced header gaskets and no change, runs great til closed loop, no SES light

 

got a TECH2 on the car, and found the left O2 sensor staying in the lean side, and the right side not sweeping just in the center. I had to replace the left bank O2 but did them both at the same time.

Runs great! DTC 48 caused by O2 sensor. Hope this helps people.