Bronco Forum - Full Size Ford Bronco Forum banner

1 - 20 of 22 Posts

·
Registered
Joined
·
637 Posts
Discussion Starter #1
I'm getting a code 126 and my 94 Bronco is running badly. It's a maf 302. I have 2 other trucks with the 5.8 and it's on the firewall by the heater box. What's going on here?
 

·
Premium Member
Joined
·
5,774 Posts
Are those other two trucks MAF?
I thought the MAP sensor was eliminated by 94
 

·
Registered
Joined
·
637 Posts
Discussion Starter #3
No they are SD but I'm getting the code for Map
 

·
House of Windsor 4ever!
Joined
·
10,512 Posts
Actually, EEC II carb and EEC III carb or CFI used a MAP/BARO sensor. I have a couple from my two CFI 5.0L wagons. The funny thing about the sensor? When you went to do a code check with the STAR tester (or, say, an MT2500 scan tool), you had to apply 20" vacuum with a pump to the BARO port to start the test. What in God's name were the engineers thinking? "We have to do it this way to keep the self-test from starting accidentally...." W.T.F.
 

·
House of Windsor 4ever!
Joined
·
10,512 Posts
Here's a pic, from some stuff I have for sale; they're the two sensors on the lower left. The left port was BARO and the right was MAP.
 

Attachments

·
Roller rockers are gay
Joined
·
19,197 Posts
Diabolic your truck still has it, and its in the same spot. It just doesn have a vacuum like on it since it's a MAF truck.
 

·
Super Moderator
Joined
·
26,022 Posts
yo D,
Which vehicle has the 126 DTC? My vision stinks and brain is shot.

Anyway, this is for posterity;

1994 PCED OBDI-A
SECTION 6A: EEC-IV Pinpoint Test Procedures
Manifold Absolute Pressure (MAP)/Barometric Pressure (BARO) Sensor
DF1 DIAGNOSTIC TROUBLE CODE (DTC) 22/126:
CHECK FOR POWER TO MAP/BARO SENSOR
DTC 22/126 indicates the Manifold Absolute Pressure (MAP)/Barometric Pressure (BARO) sensor is out of Self-Test range. Correct MAP/BARO range of measurement is typically from 1.4 to 1.6 volts.

Possible causes:
◾MAP/BARO circuit open between sensor vehicle harness connector and PCM.
◾MAP/BARO circuit shorted to VREF, SIG RTN, or GND.
◾Damaged MAP/BARO sensor.
◾Vacuum trapped at MAP/BARO sensor.
◾High atmospheric pressure.
◾Damaged PCM.
◾VREF circuit open at MAP/BARO sensor.
◾SIG RTN circuit open at MAP/BARO sensor.
•Key off.
•Disconnect the MAP/BARO sensor from the vehicle harness.
•Connect the MAP/BARO tester between the vehicle harness connector and the MAP/BARO sensor.
Insert MAP/BARO tester banana plugs into DVOM.
May as well stop here unless you have a local Ford dealer or Vehicle Electrical Shop that has the MAP tester and Break-Out-Box with proper overlays.


Also, have any EGR DTCs?
If NO;
DF8 CHECK MAP SENSOR OPERATION
•Key off.
•Disconnect vacuum supply hose from MAP sensor.
•Install vacuum pump to MAP sensor.
•Apply 18 in-Hg (61 kPa) vacuum to MAP sensor.

Does MAP sensor hold vacuum?
Yes
RELEASE vacuum. GO to DF9.

DF9 ATTEMPT TO ELIMINATE KOER DTC 22/126
•Key off.
•Plug MAP sensor vacuum supply hose.
•Start engine and maintain 1500±100 engine rpm.
•Slowly apply 15 in-Hg (51 kPa) vacuum to MAP sensor.
•While maintaining rpm, perform KOER Self-Test.

Is KOER DTC 22/126 still present?
Note: Disregard any other DTCs at this time.

Yes - REPLACE MAP sensor. CONNECT vacuum supply hose to MAP sensor. RERUN Quick Test.

NO - INSPECT vacuum supply hose to MAP sensor. SERVICE as necessary. If OK, SERVICE other KOER DTCs. If none, RETURN to Diagnostic Routines, Section 2A, to address any drive concerns.

Many parts stores will Loan a Hand Operated vacuum pump w/gauge for refundable deposit; call first for price; most deposits are for full retail $


http://www.revbase.com/BBBMOTOR/Wd/DownloadPdf?id=4906
Scroll Down
SIG-RTN GY-R is EEC IV PIN 46.
VREF BR-W is Pin 26
MAP LG-BK is Pin 45
 

·
Registered
Joined
·
637 Posts
Discussion Starter #8
My 94 Bronco is throwing code 126 but it physically does not have one.
 

·
Premium Member
Joined
·
3,988 Posts
To build on what Steve83 is saying, you probably have a different EEC than what came from the factory - or replaced the transmission. To confirm, look at your EEC Catch Code and see if there is a wire on EEC Pin #45.

See this link: MAP or BAP? Which Sensor is it?



Here is what you have...

All 1987-1995 Bronco/Truck/Van Speed Density PCM's have a MAP, with MAP Sensor Input on PCM Pin 45, VREF on Pin 26 and SIGRTN on Pin 46.

All 1994-1995 Bronco/Truck/Van MAF PCM's with E4OD Transmission do not have a MAP, except for the Bronco MAF 5.0L having the Mazda M5OD-R2.

All 1988-1993 Mustang MAF PCM's have a BAP.

All 1994-1995 Mustang MAF PCM's do not have a MAP or BAP.




Here is what you need...

When upgrading to a 1988-1993 Mustang MAF PCM, you must convert the MAP to BAP utilizing the same PCM pins.

When upgrading to a 1994-1995 Mustang MAF PCM, there is no MAP nor BAP. PCM Pin 45 is not used.

When upgrading to a 1995 F150 MAF PCM, there is no MAP nor BAP. PCM Pin 45 is not used.




 

·
Registered
Joined
·
637 Posts
Discussion Starter #10
This is very useful info. To clarify the situation.....I tuned the bronco using my AHACA strategy which I use to tune my 93 Lightning. It has the Ford Mass Air conversion and that particular conversion does have a Baro sensor. This is what threw the map code since the bronco does not have one. How or what all is necessary to install a map/Baro sensor in my 94 so that the tune will be happy and the cel will go off?
 

·
Premium Member
Joined
·
3,988 Posts
How or what all is necessary to install a map/Baro sensor in my 94 so that the tune will be happy and the cel will go off?
The MAP (Manifold Absolute Pressure) Sensor measures Vacuum Pressure for the PCM which constantly changes depending upon engine load. Typically used in EFI Speed Density, the MAP provides instananeous Manifold Pressure data which is cross-referenced with engine RPM and air temperature data to determine the engine's air mass flow rate. This information is referenced to tables which allow the PCM to determine air/fuel ratio, ignition timing, transmission line pressure and shift scheduling for higher altitude operation.

The BAP (Barometric Absolute Pressure) Sensor alternately provides Atmospheric Pressure data to the PCM. Typically used in early EFI MAF, BAP tells the PCM changes in altitude which affect air density. BAP is the essentially the same sensor as the MAP, only it is not connected to the Intake Manifold and open to the atmosphere.

To change your MAP to BAP, simply remove the vacuum line between the Intake Manifold and the MAP Sensor thus leaving the Sensor open to the atmosphere. Then cap the open vacuum port at the Intake Manifold while leaving the harness connected.

MAP/BAP connector should be Sensor Input on PCM Pin 45, VREF on Pin 26 and SIGRTN on Pin 46. Install a MAP Sensor with connector and wire it in accordingly. When I went to a 1995 WAY1 MAF EEC, my EEC Pin #45 was blank as it uses neither MAP or BAP.




 

·
Registered
Joined
·
637 Posts
Discussion Starter #12
So should I tap into the V Ref wire of the tps?
 

·
Registered
Joined
·
637 Posts
Discussion Starter #13
All V Ref returns to the same place at the test port? How does it know if it's the tps, act, or map that's bad if it all shares the same V Ref line?
 

·
Premium Member
Joined
·
3,988 Posts
The EEC separately monitors the EGR, ECT and IAT through an individual clean 5.0v Reference. Generally all have a common EEC Signal Return (ground) on EEC Pin #46.

The TPS, EVP and MAP/BAP use a common clean 5.0v Reference on EEC Pin #26 and a common EEC Signal Return (ground) on EEC Pin #46. The EEC monitors a dedicated Sensor Signal (voltage or frequency) on EEC Pin #47 (TPS), EEC Pin #27 (EVP) or EEC Pin #45 (MAP/BAP).

The Data Link Connector receives the following signals:

Pin #1 - Data-
Pin #2 - Sensor Signal Return
Pin #3 - Data+
Pin #4 - MIL Output
Pin #5 - Not Used
Pin #6 - Fuel Pump Enable




Again, the only difference between MAP and BAP is whether it is sampling Manifold or Atmospheric Pressure.




 

·
Registered
Joined
·
637 Posts
Discussion Starter #15
I finally found the switch to turn off the Baro sensor in the tune. I also turned off the knock sensor. I still have a cel for the ECT sensor and it's running a little rough. It's a new sensor so it must be in the wiring. Anyone know where it goes through the harness? According to my datalogs the ECT is working properly. That means the ECM is getting a good return signal. I'm not real sure how to interpret the code. I'm low on coolant by about a gallon so maybe that's the cause of the code.
 

·
Registered
Joined
·
139 Posts
Since 95 Trucks do not have a MAP or BAP, what is then used to measure barometric pressure(altitude) and provide the data to the EEC so it can cut back on the fuel?

To build on what Steve83 is saying, you probably have a different EEC than what came from the factory - or replaced the transmission. To confirm, look at your EEC Catch Code and see if there is a wire on EEC Pin #45.

See this link: MAP or BAP? Which Sensor is it?



Here is what you have...

All 1987-1995 Bronco/Truck/Van Speed Density PCM's have a MAP, with MAP Sensor Input on PCM Pin 45, VREF on Pin 26 and SIGRTN on Pin 46.

All 1994-1995 Bronco/Truck/Van MAF PCM's with E4OD Transmission do not have a MAP, except for the Bronco MAF 5.0L having the Mazda M5OD-R2.

All 1988-1993 Mustang MAF PCM's have a BAP.

All 1994-1995 Mustang MAF PCM's do not have a MAP or BAP.




Here is what you need...

When upgrading to a 1988-1993 Mustang MAF PCM, you must convert the MAP to BAP utilizing the same PCM pins.

When upgrading to a 1994-1995 Mustang MAF PCM, there is no MAP nor BAP. PCM Pin 45 is not used.

When upgrading to a 1995 F150 MAF PCM, there is no MAP nor BAP. PCM Pin 45 is not used.




 

·
Registered
Joined
·
637 Posts
Discussion Starter #17
I think it means it will throw the code if the engine isn't warmed up before conducting the test.
 

·
Registered
Joined
·
637 Posts
Discussion Starter #20
The newer slot meters have the IAT built in.
 
1 - 20 of 22 Posts
Top