well i finally got the computer to spit out some codes, and im trying to figure out which one is keeping the cel on... i got 22, which is the MAP sensor, 51, power steering switch, 53 tps i believe, and 54 act sensor, along with 35 which is egr related. something about egr backflow or circuit regulator?? im assuming this is the silonode on the pass. strut tower??? Im gonna set the tps later on, but it has never caused the cel light to come on on my car... all this is on a friends mustang, an he needs to get it inspected, but it wont pass with the CEL on!!! somebody please help!!!
help with codes please!!!
- Thread starter noslow5_0
- Start date
4dStang
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dvs bullet
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If it helps, when you diagnose the prob is start with the first code, the others can just be just a cascade effect off the orginal prob. Like I said if it helps
Code 22 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 and 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.
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
Code 35 EVR - EVP sensor signal is/was high - EVR
Code 53 Throttle Position sensor too high - TPS . Reset the TPS to less than .99 volt using the green & black wires to take your measurements.
Code 54 – ACT sensor out of range. Broken or damaged wiring, bad ACT sensor. Note that that if the outside air temp is below 50 degrees F that the test for the ACT can be in error.
ACT & ECT test data:
The ACT & ECT have the same thermistor, so the table values are the same
Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts
Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer. Here's the table :
68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61
Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.
50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms
Codes 35, 53, & 54 together may mean that you have a signal ground problem. All three circuits use the same black wire for signal ground.
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)
http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif
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
Code 35 EVR - EVP sensor signal is/was high - EVR
Code 53 Throttle Position sensor too high - TPS . Reset the TPS to less than .99 volt using the green & black wires to take your measurements.
Code 54 – ACT sensor out of range. Broken or damaged wiring, bad ACT sensor. Note that that if the outside air temp is below 50 degrees F that the test for the ACT can be in error.
ACT & ECT test data:
The ACT & ECT have the same thermistor, so the table values are the same
Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts
Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer. Here's the table :
68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61
Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.
50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms
Codes 35, 53, & 54 together may mean that you have a signal ground problem. All three circuits use the same black wire for signal ground.
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)
http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif
noslow5_0 said:
Sounds like you are on the right track. No ground or bad ground would affect the MAP, EGR & TPS. The computer uses the same ground circuit to put it into test mode at the diagnostic connector under the hood.
noslow5_0 said:
Bad computer? Possible, but not likely. Mstang had a similar problem, and it was the computer. I'd rather fix a broken wire by running a new one from the computer than spend $$$ for a replacement computer.
Use Tmoss's diagram and start looking for places where the ground is present. Measure resistance with the power off. Check the black wire at the MAP, EGR, ACT, ECT & TPS. Measure the resistance of the black wire between the sensors; it should be less than 1 ohm. Measure the resistance between pin 46 on the computer and the black wire on the MAP, EGR, ACT, ECT & TPS sensors. Somewhere there is a bad connection or a broken wire. The 10 pin connectors could be at fault.
To eliminate the computer as being a problem, measure between pin 46 & pins 40 & 60, which are the power grounds. You should see less than 1 ohm. Mstang had an open circuit between pins 46 and 40 & 60, which meant that he had to replace the computer.
ok, i was looking at tmoss's diagram, and it looks like the wire goes to the nuetral safety switch, then to all the other sensors... i measured the res. of the wire at the end of the signal return and with my voltmeter set on 200k it red 265... whatever that means... i think its the eqv. of .265 ohms???
noslow5_0 said:
200K Ohms is 200,000 ohms. In electronics, K=1000, so 200 x 1000= 200,000. So 265 on a 200 K ohm scale is 265,000 ohms.
Use the lowest value on the ohms function to check your wiring.
Be sure that the power is off in the circuit when you use the ohms function. If power is on, you will get wrong readings, and may damage your meter.
Measure between pin 46 on the computer and ground. You should get less than 1 ohm. You can use a safety pin to probe the pin from the backside. Don't disconnect the computer, or you will get an incorrect reading.
Measure between any of the black wires that go to the ECT, TPS, ACT, MAP, EGR sensors, Self test connector and pin 46 and you should get less than 1 ohm. You can disconnect the computer to gain access to the pins if you want to.
Signal return is computer pin 46 and is the black wire that goes to the ECT, TPS, ACT, MAP EGR & Self test connector. It does go to the neutral safety switch, but I don't think that it is important in your case.
ok, but if all else fails, i can just run a new wire to the sensors right??? it looks like a PITA, but i think it will be a lot faster then trying to check all the grounds.... the guy he bought it from said that the CEL never came on till i ran the codes, but i dont think putting the computer into diagnostics mode messed it up... it was on when he first started the car...
noslow5_0 said:
A new wire will do the job OK, you can daisy chain all of the sensor grounds together on a single wire.
Autozone or a parts store that carries Standard Motor Parts will have the pins to enable you to connect the new wire to the sensors. You have to buy the pin kits which are somewhat expensive for the number of pins you get.
Be sure to check resistance on pin 46 to pins 40 & 60 with the computer connector removed. Test across the pins & you should see less than 1 ohm. Pin 46 is wired internally to pins 40 & 60, and it has to be good or you get to replace the computer.
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