Hi Everyone, I have a question regarding voltage readings at the connector which plugs into the MAP sensor. Using http://www.kemparts.com/techtalk/tt11.asp as a reference, starting at the supply connector, I am reading 5.34v, the signal connector reads 5.34v, and the ground connector reads .3v. What is baffling me is the voltage on the signal connector and the ground. I would think both would read 0v.

I am check the voltages because when the vehicle starts up it will run good for about fifteen seconds and then begin to hunt for its idling rpm. It will surge the rpm from aprox 700 to 1300. As as it warms up, it will stabilize at around 1100 rpm and then gradually drop to 800 rpm, runnng very rough, and then catch itself and return to 1100 rpm, where the cycle starts again. Truck runs great down the highway and around town. I have replaced the MAP sensor which helped with the idle always settling in at 800 rpm, but this other problem has come about.

Your help is appreciated.

Side note, all of the ground side connectors on all sensors have a voltage of .3v. All grounding straps seem to be in place. Continuity is the same from the neg battery terminal to motor to body.

Thanks...Bill.

 

Sounds right, the wiring diagram shows 5 volts from a splice on BK/W 5 volts from the TPS on O/W and DB/LG is the signal wire.

What trouble codes have you pulled?

 

Thanks for your help.

Not quite sure I fully understand your voltages on each wire. The bk/w is a ground wire which is spliced into several other and the voltage now reads .08 v. Same is true for the o/w, splices into other o/w's and is hold 5.34v. As for the signal wire, unpluged from the MAP sensor, it reads 5.34 v. Plug it into the MAP sensor, back probe and it now reads 2.68 v. Start the vehicle, and it remains at 2.68 v. Give the motor a rev, and the voltage raises to 2.72 v. Unfortunatly, my digital volt meter does not read Hz and I cannot read the freq output, only voltage.

What just absoluted baffles me is one, the voltage at the signal wire when unplug from the MAP sensor, and two, the first thing this morning, it would not run smooth to save its life and right now, as I type, the motor is purring like a kitten, 1000 rpm. Go figure???? ERR.

I did pull KOEO code and I got the following, 11, 11, 1, 22, 63, 32, 22, 63, 32. The single dig of 1 has me scratching my head, the manual I have says there is a separater code of 111 between the KOEO and the CM output.

The ER codes were 3, 1, 21, 32, 77, 21, 32, 77. I believe 21 was cause by the engine not being fully warmed up and the 77 due to not performing the dynamic test on the TPS. I did change out the EGR valve because of the 32 code in both tests.

I also did a reset of the KOEO codes and rechecked. All I got on that test was 11, 11, 1.

 

The center connector of the plug (DB/LG) is the signal wire. Not sure if you should see 5 volts on that or not.

I have an Actron Cp-9087 sensor tester, so if this was mine i'd hook up the 9087 to the output wire & check the output. The CP-9087 will read the output in HZ.

If it tested good, i would'nt worry about the voltages.

BTW, you might want to check codes again as 3 & 1 are not valid codes.

 

I believe on the engine running test, the 3 indicates half the number of cylinders which would indicate a 6 cylinder,and the 1 indicates when the TPS full throttle is to be performed.

Where can I find an Actron tester?

 

I'm glad to say that its been awhile since i've had to pull codes on my 87 Ranger or 95 Taurus. Had to look the procedure up in my manual & you're right 3 equals 6 cylinders and 1 equals do the goose test.

Not sure exactly how the EGR controls work, but since it's idling rough & you are getting the 32/EGR code, maybe a problem in that circuit is holding the EGR open when it should'nt be.

Wish I had the pinpoint tests for the different codes.

I got lucky with the CP-9087 and found it on the Actron.com "garage sale" 7 or 8 years ago for 10 bucks. But they dont have the garage sale anymore.

Should be able to find it at Pep boys/Autozone etc..
EDIT
Does the idle smooth out if you remove the vaccum hose from the EGR

 

I just picked up an EGR vacuum switch from Ford. When I Ohm tested the original one I got a direct short and the manual say there should be 20 to 70 Ohms across the terminals. So we'll see if that helps.

 

Yeah, I would'nt be surprised if that new vac switch smoothes out the idle.

 

well, things are running smooth for the moment....I'm keeping my fingers crossed.

Thanks so much for your assistance. I will keep you up to date on any changes.

Bill.

 

Sounds good, good luck with it.