Unable to Retrieve EEC Codes

Unable to Retrieve EEC Codes
by JT (edited 09-01-2004)

Not being able to retrieve the codes is a problem. Make sure the orange 02 sensor ground wire is grounded to the stud on the compressor inlet tube to compressor housing. If that is OK, read on.

If you are troubleshooting a no-start condition, and you wish to try and pull any EEC codes from the EEC, you must ensure that you are getting power to the EEC. If the EEC is not receiving power, the engine will not start and it also will not output codes.

To check to see if the EEC is receiving power, if your vehicle is equipped with a Check Engine light, simply turn your ignition key to ON. If the Check Engine light illuminates, the EEC is receiving power. If the Check Engine light does not come on, but you recall that it used to, the EEC is either not receiving power, or you have a burned out or missing bulb.

To also determine if the EEC is receiving power, you can check the TPS sensor voltage. With the ignition key ON, unhook the Throttle Position Sensor connector and measure the voltage at the connector between the Orange/White and Black/White wires. If you see about 5 volts, the EEC is receiving power.

If you do not see 5 volts at those two wires, or if you suspect the EEC is not receiving power due to a no-start condition and a no Check Engine light illumination with the ignition key ON, then you will need to check the Integrated Relay Control module located on the passenger fender and the wiring to the module. It is the black box and contains the EEC power relay, among other relays.

   

If the EEC is receiving power but you are unable to pull any codes from the EEC, first check to see if the Signal Return circuit to the EEC is not broken. Look at the image above, and align your wire harness so that you can match it up with the image above. You want the circuit that is in the upper right corner of the bigger connector (self-test connector) labeled "Signal Return" in the above image. Hook one of your ohmmeter wires to that circuit (upper right corner of the bigger harness).


Since you probably don't have a Ford breakout box, I'll offer some advice. I would remove the EEC from the vehicle's wire harness. Use a straight pin and "plug" it into the vehicle's EEC harness side connector down the pin socket, number 46. Let me make this clear, I'm not suggesting that you use that straight pin to tap into the wire itself, nor jam it into the socket. Simply put the straight pin down the socket, easily. It is small enough to fit the socket, and not damage the connector itself. It might be loose enough that you need to jiggle it when it comes time to actually test the circuit, to ensure that straight pin is making good contact in the socket. I've done this before many times when a breakout box wasn't available, it's quick and easy. When you look at the vehicle's EEC harness connector, you will see in small print the numbers on the connector side. You will see a "41" and then should see a "60" on one row. You can probably figure out where pin 46 is from that.  

Use an ohmmeter and hook the other side of the ohmmeter to that straight pin in pin number 46. You shouldn't see much, if any, resistance. If you get large resistance, then you will need to repair that wire/circuit and that is probably the source of many of your issues.  If there is minimal resistance on that circuit, then test the Self-Test Input circuit. The Self-Test Input circuit is in that smaller self-test connector on the driver side fender, the 1-wire connector. Hook one side of your ohmmeter to that wire, then hook the other side of your ohmmeter to pin number 48 of the vehicle's EEC wire harness. Again, you should see little to no resistance. If you do, you will need to repair that wire, and that should put you one step closer to getting some info out of the EEC.

One other test you can do that is quicker, but may be less effective, is to remove the throttle position sensor wire harness and then measure the voltage at the wires (orange/white and black/white) on the vehicle harness side of the throttle position sensor. Do you see 5 volts there? This test is sometimes used to determine if the EEC is getting power, but we already know that it is. Otherwise the engine would not start. Instead, this will tell us if there is a break on that signal return line.

If all of the above checks out fine and you're still unable to pull any trouble codes, and the vehicle does start, then you need to start checking the Voltage Reference circuit. This circuit supplies about 5 volts to the Throttle Position Sensor, the Barometric Pressure Sensor, and the Vane Air Flow Sensor. It also is used to get the EEC into diagnostic mode to pull any trouble codes. If this circuit does not have 5 volts on it, not only will you have drivability issues because those above mentioned sensors will not be able to provide information to the EEC, but you also will not be able to get the EEC into the diagnostic mode.

If you did not check the voltage on the Orange/White and Black/White wires at the Throttle Position Sensor with the ignition key ON with the sensor disconnected, then do so now. You should see about 5 volts there. If you do not, then it is possible one of the sensors is shorting out the circuit. Unhook the Vane Air Meter connector and the Barometric Pressure Sensor connector. Now check the voltage at the Orange/White and Black/White wires with the sensors disconnected. If you see 5 volts, then plug in the Barometric Pressure Sensor connector and the Vane Air Meter Sensor one at a time and note which sensor drops the 5 volts. That sensor that does this, is either faulty or there is a short in the circuit.  

If you still do not see 5 volts at the Orange/White and Black/White wires, then with the Throttle Position Sensor, Barometric Sensor and Vane Air Meter Sensor still disconnected, go back to the EEC and check some ohm values.

Hook one side of your Ohmmeter to the Pin number 26 of the harness connector where the EEC connects. Now check the follow resistances:

Pin 20 (with Pin 26)

Pin 40 (with Pin 26)

Pin 46 (with Pin 26)

Pin 60 (with Pin 26)

If any circuit is less than 5 ohms, there is a short to ground and that needs to be repaired. If all circuits read over 5 ohms, then it is possible your EEC is faulty. EEC failures are rare, but can happen due to electrical spikes that result from improper jump starting or unhooking the battery while the engine is running.

Hope this helps. Let us know the results so that we can further help.  

By JT (edited 09-01-2004).]