codes
- Thread starter Doc90
- Start date
Code 21 – ECT sensor out of range. Broken or damaged wiring, bad ECT sensor.
Note that that if the outside air temp is below 50 degrees F that the test for the
ECT can be in error.
The ECT sensor has absolutely nothing to do with the temperature gauge. They are
different animals. The ECT sensor is normally located it the RH front of the engine in
the water feed tubes for the heater.
The ACT & ECT have the same thermistor, so the table values are the same
ACT & ECT test data:
Use Pin 46 on the computer for ground for both ECT & ACT to get most accurate
readings.
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.
Voltages may be measured across the ECT/ACT by probing the connector from
the rear. A pair of safety pins may be helpful in doing this. Use care in doing it
so that you don't damage the wiring or connector.
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
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.
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
Diagram courtesy of Tmoss & Stang&2birds
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif
Code 33 - Insufficient EGR flow detected.
Look for vacuum leaks, cracked vacuum lines, failed EGR vacuum regulator. Check to see if
you have 10” of vacuum at the EGR vacuum connection coming from the intake manifold.
Look for electrical signal at the vacuum regulator solenoid valves located on the rear of the
passenger side wheel well. Using a test light across the electrical connector, it should
flicker as the electrical signal flickers. Remember that the computer does not source any
power, but provides the ground necessary to complete the circuit. That means one side of
the circuit will always be hot, and the other side will go to ground or below 1 volt as the
computer switches on that circuit.
Check for resistance between the brown/lt green wire on the EGR sensor and pin 27 on the
computer: you should have less than 1 ohm.
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif
http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif
EGR test procedure courtesy of cjones
to check the EGR valve:
bring the engine to normal temp.
connect a vacuum pump to the EGR Valve
apply 5in vacuum to the valve.
if engine stumbled or died then EGR Valve and passage(there is a passageway through
the heads and intake) are good.
if engine did NOT stumble or die then either the EGR Valve is bad and/or the passage is
blocked.
if engine stumbled, connect vacuum gauge to the hose coming off of the EGR Valve
snap throttle to 2500 RPM (remember snap the throttle don't hold it there).
did the vacuum gauge show about 5in vacuum?
if not, check for manifold vacuum at the EGR vacuum valve.
if you have manifold vacuum then connect vacuum gauge to the EGR valve side of the
vacuum valve and snap throttle to 2500 RPM.
should read about 5in vacuum
The operation of the EGR vacuum regulator can be checked by using a test light applied
across the wiring connector. Jumper the computer into self test mode and turn the key on
but do not start the engine. You will hear all the actuators (including the EVR vacuum
regulator) cycle. Watch for the light to flicker: that means the computer has signaled the
EGR vacuum regulator successfully.
Codes 94 & 44 - AIR system inoperative - Air Injection. Check vacuum lines for leaks, &
cracks. Disconnect the big hose from smog pump: with the engine running you should feel
air output. Reconnect the smog pump hose & apply vacuum to the first vacuum controlled
valve: Its purpose is to either dump the pump's output to the atmosphere or pass it to the
next valve. The next vacuum controlled valve directs the air to either the cylinder heads
when the engine is cold or to the catalytic converter when the engine is warm. Disconnect
the big hoses from the back side of the vacuum controlled valve and start the engine.
Apply vacuum to the valve and see if the airflow changes from one hose to the next.
The two electrical controlled vacuum valves mounted on the rear of the passenger side
wheelwell turn the vacuum on & off under computer control. Check to see that both valves
have +12 volts on the red wire. Then ground the white/red wire and the first solenoid
should open and pass vacuum. Do the same thing to the light green/black wire on the
second solenoid and it should open and pass vacuum.
Remember that the computer does not source power for any actuator or relay, but
provides the ground necessary to complete the circuit. That means one side of the circuit
will always be hot, and the other side will go to ground or below 1 volt as the computer
switches on that circuit.
The computer provides the ground to complete the circuit to power the solenoid valve that
turns the vacuum on or off. The computer is located under the passenger side kick panel.
Remove the kick panel & the cover over the computer wiring connector pins. Check Pin 38
Solenoid valve #1 that provides vacuum to the first Thermactor control valve for a switch
from 12-14 volts to 1 volt or less. Do the same with pin 32 solenoid valve #2 that provides
vacuum to the second Thermactor control valve. Starting the engine with the computer
jumpered to self test mode will cause all the actuators to toggle on and off. If after doing
this and you see no switching of the voltage on and off, you can start testing the wiring
for shorts to ground and broken wiring. An Ohm check to ground with the computer
connector disconnected & the solenoid valves disconnected should show open circuit
between the pin 32 and ground and again on pin 38 and ground. In like manner, there
should be less than 1 ohm between pin 32 and solenoid valve #2 and pin 38 & Solenoid
valve #1.
If after checking the resistance of the wiring & you are sure that there are no wiring faults,
start looking at the solenoid valves. If you disconnect them, you can jumper power &
ground to them to verify operation. Power & ground supplied should turn on the vacuum
flow, remove either one and the vacuum should stop flowing.
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host)
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif
http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif
Note that that if the outside air temp is below 50 degrees F that the test for the
ECT can be in error.
The ECT sensor has absolutely nothing to do with the temperature gauge. They are
different animals. The ECT sensor is normally located it the RH front of the engine in
the water feed tubes for the heater.
The ACT & ECT have the same thermistor, so the table values are the same
ACT & ECT test data:
Use Pin 46 on the computer for ground for both ECT & ACT to get most accurate
readings.
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.
Voltages may be measured across the ECT/ACT by probing the connector from
the rear. A pair of safety pins may be helpful in doing this. Use care in doing it
so that you don't damage the wiring or connector.
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
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.
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
Diagram courtesy of Tmoss & Stang&2birds
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif
Code 33 - Insufficient EGR flow detected.
Look for vacuum leaks, cracked vacuum lines, failed EGR vacuum regulator. Check to see if
you have 10” of vacuum at the EGR vacuum connection coming from the intake manifold.
Look for electrical signal at the vacuum regulator solenoid valves located on the rear of the
passenger side wheel well. Using a test light across the electrical connector, it should
flicker as the electrical signal flickers. Remember that the computer does not source any
power, but provides the ground necessary to complete the circuit. That means one side of
the circuit will always be hot, and the other side will go to ground or below 1 volt as the
computer switches on that circuit.
Check for resistance between the brown/lt green wire on the EGR sensor and pin 27 on the
computer: you should have less than 1 ohm.
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif
http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif
EGR test procedure courtesy of cjones
to check the EGR valve:
bring the engine to normal temp.
connect a vacuum pump to the EGR Valve
apply 5in vacuum to the valve.
if engine stumbled or died then EGR Valve and passage(there is a passageway through
the heads and intake) are good.
if engine did NOT stumble or die then either the EGR Valve is bad and/or the passage is
blocked.
if engine stumbled, connect vacuum gauge to the hose coming off of the EGR Valve
snap throttle to 2500 RPM (remember snap the throttle don't hold it there).
did the vacuum gauge show about 5in vacuum?
if not, check for manifold vacuum at the EGR vacuum valve.
if you have manifold vacuum then connect vacuum gauge to the EGR valve side of the
vacuum valve and snap throttle to 2500 RPM.
should read about 5in vacuum
The operation of the EGR vacuum regulator can be checked by using a test light applied
across the wiring connector. Jumper the computer into self test mode and turn the key on
but do not start the engine. You will hear all the actuators (including the EVR vacuum
regulator) cycle. Watch for the light to flicker: that means the computer has signaled the
EGR vacuum regulator successfully.
Codes 94 & 44 - AIR system inoperative - Air Injection. Check vacuum lines for leaks, &
cracks. Disconnect the big hose from smog pump: with the engine running you should feel
air output. Reconnect the smog pump hose & apply vacuum to the first vacuum controlled
valve: Its purpose is to either dump the pump's output to the atmosphere or pass it to the
next valve. The next vacuum controlled valve directs the air to either the cylinder heads
when the engine is cold or to the catalytic converter when the engine is warm. Disconnect
the big hoses from the back side of the vacuum controlled valve and start the engine.
Apply vacuum to the valve and see if the airflow changes from one hose to the next.
The two electrical controlled vacuum valves mounted on the rear of the passenger side
wheelwell turn the vacuum on & off under computer control. Check to see that both valves
have +12 volts on the red wire. Then ground the white/red wire and the first solenoid
should open and pass vacuum. Do the same thing to the light green/black wire on the
second solenoid and it should open and pass vacuum.
Remember that the computer does not source power for any actuator or relay, but
provides the ground necessary to complete the circuit. That means one side of the circuit
will always be hot, and the other side will go to ground or below 1 volt as the computer
switches on that circuit.
The computer provides the ground to complete the circuit to power the solenoid valve that
turns the vacuum on or off. The computer is located under the passenger side kick panel.
Remove the kick panel & the cover over the computer wiring connector pins. Check Pin 38
Solenoid valve #1 that provides vacuum to the first Thermactor control valve for a switch
from 12-14 volts to 1 volt or less. Do the same with pin 32 solenoid valve #2 that provides
vacuum to the second Thermactor control valve. Starting the engine with the computer
jumpered to self test mode will cause all the actuators to toggle on and off. If after doing
this and you see no switching of the voltage on and off, you can start testing the wiring
for shorts to ground and broken wiring. An Ohm check to ground with the computer
connector disconnected & the solenoid valves disconnected should show open circuit
between the pin 32 and ground and again on pin 38 and ground. In like manner, there
should be less than 1 ohm between pin 32 and solenoid valve #2 and pin 38 & Solenoid
valve #1.
If after checking the resistance of the wiring & you are sure that there are no wiring faults,
start looking at the solenoid valves. If you disconnect them, you can jumper power &
ground to them to verify operation. Power & ground supplied should turn on the vacuum
flow, remove either one and the vacuum should stop flowing.
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host)
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif
http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif
94 and 44 are usually output because the car was not fully warmed up (or you have the smog valves disconnected). clear codes by starting the self-test and disconnecting the code reader (or jumper wire) as the codes are being output (not after, but during), or simply disconnect the battery for about 15 min. then, to make sure the engine is at full operating temp, run the engine at 2000 rpm for 2 minutes. recheck codes, and if the 94 and 44 are back, do the diagnostic procedure for those codes that jrichker outlined.Doc90 said:
regarding the 20, if this was the last code output by the scanner it sounds as if its a code for the "cylinder balance" portion of the test. 20 means you have a miss on cylinder #2. check your plug and plug wire, if those are ok let us know. it may be necessary to test the injector. good luck
