Code 14 - MAP sensor

[bigshrimpin]

I think this is the last of my problems :) at least I sure hope it is.

 

I'm getting an error . . . Code 14 about voltage being too low or high for the MAP sensor . . . does this mean the MAP sensor needs to be replaced or that some input signal to the MAP sensor is off? is there anyway to troubleshoot this problem without buying a new MAP sensor?

[brigarpeon]

SO we begin Young Padawan

To test, using a voltmeter with the ignition on/engine off, voltage at terminal B should be 4 - 5 volts. The voltage should drop to 1.5 - 2.1 volts with a HOT, neutral idle engine. Supply voltage can be checked at terminal C with the ignition on. Voltage there should be 5 volts + or - 0.5 volts (Terminal A is the ground wire).

 

What does it do? Compares ambient barometric pressure during start-up (cranking) to engine load while engine is running. The ECU computes that information and adjusts the air-fuel mixture accordingly.

[bigshrimpin]

All right I got there . . . 4.88 Volts ignition on.

Engine started, warmed up at idle . . . output hovers at 1.66volts (down to 1.52 . . . up to 1.88).

 

Is it safe to say now that the MAP sensor is behaving properly?

[brigarpeon]

I would say it is working but performing poorly at the low end of it's capability. This is most likely due to an extended period of operation, it's getting old. Something like how a spark plug can cause your engine performance and mileage to go down as it becomes older and more worn. You can clean it and regap it and it will work better but you don't regain full mileage and performance until you put in new.

Since the startup voltage is normal, the computer side is OK but, the map sensor (manifold) sends the signal so it may be headed South.

[bigshrimpin]

Doh - I'm an idiot :) Turns out that I accidentally dropped two of the spark plugs before I put them back in for the last time. I didn't notice . . . but it must have landed arse end down . . . there was no gap at all on plug #1. regapped the plug back to .35 . . . no more code 14????? The truck purrs like a kitten!!! with the new injectors, cap, rotor, o2 sensor, and total douche of the fuel system.

 

I step on the gas and I can light up the tires . . . wohoooo!!

 

Thanks everyone for all your help . . . I learned a ton working through this "problem".

[SomeNew Name]

how are you pulling the codes? what type of reader are you using? and where did you get it

[maddzz1]

how are you pulling the codes? what type of reader are you using? and where did you get it

 

I think hes doing it using the key cylinder. You have to turn the lock cylinder a certain way and the check engine light will flash a different number of times to give the code. Not sure what year you have but this is from hornbrod:

 

Reading Computer Codes

On 1991 to1997 models ( 1984 to 1986 V6 models as well as 1998 to 2002 follow ) you have a way of reading for fault codes which can be accessed without any scanners like other models by reading how the check engine light flashes. Start by turning the ignition key to the last stop before it starts, on and off three times within 5 seconds ending in the on position on the third time, ( i.e. on, off, on, off then on and hold ). The check engine light will start to flash quickly with a small pause in between then a medium pause to indicate the next number in the to digit number and then a long pause before the next set of flashing for the next code. If all is well you will get a code 55 which would read like this: 5 fast flashes, medium pause then a further 5 flashes. This is how all codes end with is this 55 code if you have air conditioning or with a code 33 without and any other codes would have been before it separated by a long pause. The codes will remain after this test so you can cycle through it as many times as it takes to read them. After a problem has gone the code will be removed after 50 on off key cycles or if the battery left disconnected over night which will cause a code 12 though.

[bigshrimpin]

Yup . . . that's how I was reading them.

[HOrnbrod]

how are you pulling the codes? what type of reader are you using? and where did you get it

 

I think hes doing it using the key cylinder. You have to turn the lock cylinder a certain way and the check engine light will flash a different number of times to give the code. Not sure what year you have but this is from hornbrod:

 

Reading Computer Codes

On 1991 to1997 models ( 1984 to 1986 V6 models as well as 1998 to 2002 follow ) you have a way of reading for fault codes which can be accessed without any scanners like other models by reading how the check engine light flashes. Start by turning the ignition key to the last stop before it starts, on and off three times within 5 seconds ending in the on position on the third time, ( i.e. on, off, on, off then on and hold ). The check engine light will start to flash quickly with a small pause in between then a medium pause to indicate the next number in the to digit number and then a long pause before the next set of flashing for the next code. If all is well you will get a code 55 which would read like this: 5 fast flashes, medium pause then a further 5 flashes. This is how all codes end with is this 55 code if you have air conditioning or with a code 33 without and any other codes would have been before it separated by a long pause. The codes will remain after this test so you can cycle through it as many times as it takes to read them. After a problem has gone the code will be removed after 50 on off key cycles or if the battery left disconnected over night which will cause a code 12 though.

 

On this statement is says: "1984 to 1986 V6 models as well". Has anyone actually verified that this works on the 2.8L LR2 GM engines found in 86 MJs and 84-86 XJs? I've never tried it.

[beaterjeep]

On this statement is says: "1984 to 1986 V6 models as well". Has anyone actually verified that this works on the 2.8L LR2 GM engines found in 86 MJs and 84-86 XJs? I've never tried it.

I'll give it a try early next week with the MJ15 and report back on if it works or not.

[SomeNew Name]

I've tried to do the Key Cylinder thing, but it doesn't work for me.. and I followed the ionstructions to the letter..... 1990 4.0 aw4

[HOrnbrod]

I've tried to do the Key Cylinder thing, but it doesn't work for me.. and I followed the ionstructions to the letter..... 1990 4.0 aw4

 

Won't work on Renix 4.0L. :oops: I'm trying to get someone to try it with the 84-86 2.8L V6 to see if the statement I cut and pasted originally is true for these models.

[mvusse]

On mu 1994 Suburban with a GM TBI 350 (OBD I), you just short 2 terminals on the diagnostic port and turn the ignition on. Then you count flashes of the Check Engine light to read the codes.

 

I'm assuming the 2.8V6 is the same.

[HOrnbrod]

On mu 1994 Suburban with a GM TBI 350 (OBD I), you just short 2 terminals on the diagnostic port and turn the ignition on.

 

I'm assuming the 2.8V6 is the same.

 

:dunno: