My 95 threw a code this week. 1123, Secondary Air Injection system. How does it know that the system is not working, or is not there? There does not seem to be any current sensing going on of the relay, or the pump. Does it just look at the O2 sensor signal and decide that it is running too rich so the secondary air pump must not be working?
Nobody knows? What is the mechanism by which the computer can throw a Secondary air injection code? The 95 schematic does not show a current sensing scheme because + side goes to relay output, - side goes straight to ground for both the air pump and the solenoid controlling the air valve. The only thing left is the O2 signal being "rich" I have the error code, I reset it, I turn the engine on, the error immediately comes back.
The purpose of the secondary air system (as you may know) is to supply supplemental oxygen until the CAT's warm up. So, it would seem that the O2 sensors would know this except a 95 only has pre CAT O2 sensors (as you know). IIRC, the pump filter can get dirty and cause a current overload so perhaps that is where the code is coming from. Guessing here: perhaps a bad relay can be detected by the ECU (lack of change in state?)
This is a weird one. I made the whole assembly work and check that there is air flow at the output of the air valve at the air pump. I could check the air After the check valve at the far bank. Perhaps the pump is not putting out enough flow to overcome the check valve. So, are we in agreement that it is the O2 sensor signal that the computer is using to guess at the secondary air injection system health?
I also doubt the o2 sensors would throw the secondary air injection code. Remember the engine is in open loop when stone cold so no input from o2 until closed loop fuel control. MCJoe offers good information. If the code is back straight away,a current draw test on the pump would be the next thing to check it is in good working order. The pumps do have a history of failing. Cheers Andy.
I hate to post guesses but in this case I'll just add some content that you can take as you will. According to the WSM the secondary air system is activated when lambda control is not active, due to being damaged, disconnected or because O2 sensors have not heated up. So if the code returns immediately on cold start, I can not see how the O2 sensor would be the trigger since they would not yet be active. Also, the WSM seems to imply that once the O2 sensors heat up and the ECU enters closed loop mode, the air injection is turned off. Now, if you can believe the WSM...... \
its not coming from the o2. Its being thrown by the air injection circuit. Sometimes the rubber hose on the main pipe splits in hard to see places..
The mystery here is what signal is being sent to the ECU to throw the code? Mitch, along with John's comments, I'd check when the pump relay turns on and off. You know it's running but does it shut off? You also made mention that one bank is light on air? Maybe add some compressed air to see if any change occurs.
OK found it. There are 2 ECUs on the 95. Bank 1, the right bank pin 21 activates the Secondary Air Valve solenoid, while Bank 2, the left bank pin 21 activates the bypass valve solenoid. There is "status sensing" by the ECU monitoring either the voltage or the current at pin 21 when it tries to activate that signal. If there is any sign of trouble, either computer will throw a CEL 1123 code. So a 1123 code on bank 1 is the code for secondary air valve. The same code 1123 on bank 2 (what I got) is the error code for bypass valve which has nothing to do with secondary air injection. Fooking Italian !!!
Mitchell am I missing something because should the pin 21 be a cam phase based on your pinout description of the motronic in the diy thread?
Grant My 1995 355 is OBD1, with two 55 pin ECU controllers, left and right. My 1996 355 is OBD2 with one 88 pin ECU controller behind the passenger seat. The OBD1 controller pin 21 is for Secondary air injection. The OBD2 controller pin 21 is cam phase. Now, my 1994 factory challenge with OBD1 and 2 controllers is slight different still….
Yes, but aren't solenoids faults are supposed to throw a 2123 code? I believe 1123 is the air pump relay and that appears to be controlled by the left ECU, so a 1123 code on the left ECU should be the air pump relay. Only way to tell for sure would be to pull the relay on a working car and see what code appears and where.
After carefully tacking the wires I agree that P21, bank1 controls the relay for the air pump and the solenoid for the secondary air. P21, bank2 controls the solenoid for the bypass valve. Still wondering about what code 2123 is for?
