Still P0101

[RAF7789]

So the P0101 has still got me . The MAP and MAF have both been switched out by known good ones, the code returns. The MAP still reads about 7.0-7.3inHg and does not change with condition change.

Car reads 7.0-7.3 inHg regardless of if the engine is running. There has been several instances where the MAF reading was other than zero after the car had been shut off, key still in.

All the wires tested continuous and i was wondering where to go from here? Take it in? What doe you guys think?

[Injuneer]

Without going back in detail through the other thread.....

-have you checked the MAP sensor wiring for the correct voltage. 5.0V between the gray and black wires, a variable voltage between the light green and black wires - close to 5V with the key on engine off, and about 1.5V with the engine idling.

-have you checked the frequency signal from the MAF sensor? I posted the typical values for idle in the other post. You mention that at some times the MAF sensor reads a value even though the engine is shut off. Is that value around 470gps? If so, that would indicate an intermittent "open" in the MAF wiring.

[RAF7789]

Fred it has been anywhere from .900-1.045 lb/sec.

and (.470 kg)(2.205 lb/kg)= about 1.036 lb/sec. (as long as that is a mass flow rate grams/sec not the vol. flow rate gall'n/sec.) I will further investigate the MAF and MAP wires and make sure nothing is burned through, cracking, resting on I/manifold etc.

Another development made today: when i unplug the MAP at idle, the scanner reads about 2.3 inHg....no fluctuation in the reading with any throttle... Is that normal? The sensor being unplugged, and still giving a reading while running?

I have a feeling my problem lies with the MAP circuit somewhere, because my car will not run if I unplug the MAF sensor (thus forcing into speed density mode, and relying on readings from IAT, MAP, VSS, and tables within the programming) IAT and VSS readings are normal. Will keep updated

PS: what should the MAP reading be in key-on, engine-off condition? 29-30 inHg? (1 atm~30 inHg)

[RAF7789]

phew! found that the pink wire from the MAF was melted ever so slightly on the i/manifold. so i replaced a small length of the wire there. However that is not the signal wire though... it does not give false readings with the engine off and key on anymore. But still have P0101 pending and SES light on.

i made a big mess of me wiring harness. gotta buy some convoluted tubing to put everything back in order.

MAP still reads 7.0-7.3 inHg while plugged in, key on,engine off or on. and 2.3-2.9 inHg while unplugged. The MAP signal wire (green wire) tested continuous, but all that means is that the wire is not totally severed. however it could still have burned or cut through somewhere and is grounding out through the path of least resistance.

anyways, just theorizing out loud.. any ideas, feel free!

[97LT4SS]

I would replace the pigtail going to the MAF, but make sure you solder the connections.

Good luck

[RAF7789]

Thank you, I've already done that.. When the MAP is ungrounded (while i was replacing the ground wire, i had it off) it was reading 29.9-30inHg, with the engine off key on. But as soon as i ground it, it goes back to 7.0-7.3inHg. When the MAP is out of the manifold, but still plugged in, it reads 7.0-7.3inHg (grounded) and 29-30 inHg(ungrounded).

I have tried that with a known good MAP sensor, and the same results occur. I have replaced all three wires going from the MAP to PCM (signal, 5v source, and for the ground, i put the ground wire coming from the IAT sensor in with the MAP ground; as to be in accord with the factory configuration) I have replaced the MAF signal wire as well. All of these were attempts to bypass a short or ground in the circuit.

I am 100% certain that all of the wires are going to the right bank in the right connector of the PCM.

The scanner i am using scans other MAP sensors and the readings are in reasonable ranges.

What a challenge

I never checked my MAF sensor fuse, but i will right now. If that were the problem then there would not be voltage supplied to the MAF at all right?

How would i know if i had to replace the PCM?

[Injuneer]

I have tried that with a known good MAP sensor, and the same results occur. I have replaced all three wires going from the MAP to PCM (signal, 5v source, and for the ground, i put the ground wire coming from the IAT sensor in with the MAP ground; as to be in accord with the factory configuration) I have replaced the MAF signal wire as well. All of these were attempts to bypass a short or ground in the circuit.

What about the other sensors wired together with the MAP? In the 95 diagrams that Shoebox has on his site, the A/C EVAP temp and pressure sensors share the +5V reference wire, and the black ground wire?

Have you verified you have 5V key on on the gray wire? What is the voltage between the green wire and the black wire with the harness connector unplugged?

[RAF7789]

5v between MAP signal and black wire. yesterday I ended up switching back to the original ground wire, because after reviewing the wiring schematics on shoebox's site, i realized i was bypassing several sensor grounds. which is a no no. I think it was the A/C press and A/C temp sensors, and IAT(?).

Does the 5v between green and black conclude anything? Other than the sensor is getting proper voltage?

Also, i had a question about the MAF pink wire: it goes to the PCM Ignition feed...? what purpose does this serve? other than consolidation of wiring.

[aldaran]

Wow. I had the same code on my Silverado and all it was air escaping from the housing due to a loose clamp. Light turned off after three successful drives in which the error no longer occurred. I wish it was that simple with your application.

[RAF7789]

If anyone would like to call me regarding this, feel free : (408) 483-4680

So here is the exact run down of the situation:

MAP is known to be in new condition, MAF is also in working condition, the only code popping up is P0101.

MAP reading, regardless of engine conditions (either on or off, load, idle) 7.0-7.3 inHg

With MAP unplugged, sensor reading: 2.3inHg

With MAP plugged in, installed or uninstalled, engine off or running: around 30inHg

MAF reading, normal, within plausible range and changes with conditions.
All other sensor readings are within range and normal.

Going to call some service departments and repair shops next week.

[RAF7789]

just saw something alarming....P1371...


I'll replace the red/blk wire tomorrow morning in hope to cure the problem. My previous distributor replacement was the Dynaspark. If i need to replace that again i hope they'll take care of the replacement.. anyone know the warranty on those? Their website was uninformative of such info... Fingers crossed. Wish me luck!!!!

[aldaran]

Good Luck!

[RAF7789]

The ICM wires were mangled up right at the connector with bare wires coming out of their insulation. So i went ahead and replaced that, p1371 didn't come back after replacing the connector and a small length of all of their wires.

I may be in good shape right now! Still got that MAP bug though. Any thoughts on that? i'm thinking it's a ground issue. But the MAP ground is the same as the IAT and two A/C sensor grounds, and all of them are working fine except the MAP.

with the map ungrounded, the sensor reads a reasonable value, but as soon as i ground it (either through the ground wire or the block/body ground) it goes back to 7.0-7.3"Hg.

There seems to be a rather technical problem here. Any troubleshooting ideas?

[RAF7789]

p1371 returns after long periods of driving; when the car is hot hot. tackling the low res wire.