Mustang Code Troubles

[RangerJoe]

Following the advice of several tuners, I removed my Diablo chip after building my stroker. They advised that I should not try to run my 302 chip for my 331, and that I should have it retuned...so the chip is out and I'm running on the stock a9l for the time being.

Pulled the KOEO codes today. Got the following:
22 34 81 82 84 85

The car has the EGR deleted, no TAB solenoids on the passenger's side firewall and no charcoal canister. I know that a chip can turn off many of these codes, so I don't know what the previous owner had done when the chip was burned.

I know 22 is the BAP sensor. I know 34 and 84 are EGR related. I know 81 and 82 are TAB solenoid related. I know 85 has to do with the charcoal canister. With exception to code 22, can the rest of these be simply turned off with a chip, or will they cause problems. I have no cats by the way.

As far as code 22 goes, I have checked both wires and they are getting around 5v and the signal return wire seems to have ground. Is my next step to replace the BAP, or could it be related to the other codes?

Thanks in advance! Oh yeah, car surges every once in a while, maybe a couple of hundred RPMs, but it usually flattens out and runs just fine after a few seconds or a minute.

Thanks

 

[jrichker]

It sounds like you have done your homework, but just for the sake of review, here's the code 22 test path....


On a Mass Air car, the MAP sensor vents to open air and actually acts to sense the barometric pressure. It becomes a Barometric Air pressure sensor. It's purpose is to set a baseline for the computer to know the height above sea level. The fuel requirements decrease as altitude increases, since the atmospheric pressure decreases. As altitude increases, it leans out the fuel flow to compensate for less oxygen in the air.

Disconnecting the MAP or BARO sensor will set code 22.

Misconnecting the BARO sensor to vacuum on a Mass Air car will cause the computer to lean out the fuel mixture.

Code 22 or 126 MAP (vacuum) or BARO signal out of range. The MAP or BARO sensor is pretty much the same sensor for both Mass Air & Speed Density cars. The main difference is where it is connected. Mass Air cars vent it to the atmosphere, while Speed Density cars connect it to the intake manifold vacuum. Its purpose is to help set a baseline for the air/fuel mixture by sensing changes in barometric pressure. The MAP or BAP sensor puts out a 5 volt square wave that changes frequency with variations in atmospheric pressure. The base is 154 HZ at 29.92" of mercury - dry sunny day at sea level, about 68-72 degrees. You need an oscilloscope or frequency meter to measure it. There a very few DVM with a price tag under $40 that will measure frequency, but there are some out there.

The MAP/BARO sensor is mounted on the firewall behind the upper manifold on 86-93 Mustangs.

Baro or MAP test using frequency meter - run the test key on engine off. The noise from the ignition system will likely upset the frequency meter. I used a 10 x oscilloscope probe connected from the frequency meter to the MAP/BAP to reduce the jitter in the meter's readout.

If it is defective, your air/fuel ratio will be off and the car’s performance & emissions will suffer

Some basic checks you can make to be sure that the sensor is getting power & ground:
Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter.
Check the resistance between the black/white wire on the MAP/BARO sensor and then the black/white wire on the EGR and the same wire on the TPS. It should be less than 1 ohm. Next check the resistance between the black/white wire and the negative battery cable. It should be less than 1.5 ohm.

The following power on check requires you to turn the ignition switch to the Run position.
Use a DVM to check for 5 volts on the orange/white wire. If it is missing, look for +5 volts at the orange/white wire on the TPS or EGR sensors. Use the black/white wire for the ground for the DVM.


If the wiring is good, the code 22 isn't related to any of the other codes. The code 34 could be a bad signal ground (black/white wire). The EGR sensor and the Baro/Map sensor use the same black/white wire ground and if it goes bad, both sensors will set codes. In your case, that probably isn't true since you have deleted the EGR.

 

[RangerJoe]

TTT

 

[RangerJoe]

Solution

For anyone having this trouble...As stated above, I checked my voltage and signal return, and they checked out good. Without having anyway to check the frequency of the Map Sensor, I went to a local junk yard and got one for $20. Plugged it in before paying the guy, and bam! No check engine light! Looks like it was the sensor after all. Things are looking up for the time being!