P0412 Secondary Air Delete

On my Mk4 with 1996 4.6 DOHC I am getting a P0412 error because the Secondary Air system has been removed. I have searched several forums for a solution and found that I can place a resistor into the circuit to fool the PCM into thinking the AIR system is still there.

My problem is that I do not know what size resistor/s/ and where to place them.

I know the AIR uses pin 5 and pin 70 on the PCM. So I am guessing two resistors connected to these two pins and guessing that one end of each resistor is connected to one of these pins and the other end to ground. But I am only guessing.

Can anyone help me?

CamrCobr

Camrcobr,

If the AIR system you are referring to is solenoid activated, 75 Ohm, 2 Watt would be more that enough to fool the EEC into thinking that the solenoid coil is still there . . .

IF those two pins (5 and 70) go to a connector, one resistor between the two wires is the answer. Verify that pin 5 and pin 70 go to a solenoid coil connector together. IF they are two separate circuits, you'll need to figure out where they "return to" - not necessarily ground, and then place resistors from pin 5 wire to ?? and pin 70 wire to ??.

Doc

Thank you Big Blocker!

This AIR system is electrical. The two PCM pins go to a 4 connector SSR (Solid State Relay). The other two places on the SSR go to Always Hot +12V and Ground. These 4 wires go to two AIR circuits, One which includes the bypass valve and the other the pump.

From studying the service manual it “appears” Pin 70 is the trigger….when the PCM connects PCM pin 70 to ground inside the PCM, this completes the circuit to power the Bypass and causes the SSR (relay) to send +12V to the other circuit to power the pump. Pin 5 is in this second circuit and serves as the AIR monitor to tell the PCM all is working. Or at least that is what I am thinking.

If all that guessing is right then I should be able to fool the PCM into thinking the AIR is still there and working by finding a +12V power source wire, placing a resistor (Imitating a load) onto the wire and connecting the other end of the wire to pin 5 and then on to Pin 70.

+12v------->10k resistor-------->pin 5-------->pin 70

(pin 70 will become ground when PCM signals AIR ON thereby completing the circuit)

Hopefully by connecting pin 5 into the mix, pin 5 will tell the PCM that a Load is there when AIR is Turned ON and no load when turned off……..but I am not really sure I will be handling pin 5 right and if not I could get P1413 and/or P1414.
Here is a diagram of my system (which is removed from the car):

Attachment 100075

And here is the info on Trouble codes:

Secondary Air Injection (AIR) System Monitor Electric Air Pump System

The Secondary Air Injection (AIR) System Monitor is an on-board strategy designed to monitor the proper function of the secondary air system. The AIR Monitor for the Electric Air Pump system consists of two monitor circuits: an AIR circuit to diagnose problems with the primary circuit side of the Solid State Relay (SSR), and an AIR Monitor circuit to diagnose problems with the secondary circuit side of the Solid State Relay. A functional check is also performed that tests the ability of the AIR system to inject air into the exhaust. The functional check relies upon HO2S sensor feedback to determine the presence of air flow. The monitor is enabled during AIR system operation and only after certain base engine conditions are first satisfied. Input is required from the ECT, IAT, and CKP sensor, and the HO2S Monitor test must also have passed without a fault detection to enable the AIR Monitor. The AIR Monitor is also activated during on demand self-test.

1. The AIR circuit is normally held high through the SAIR Bypass solenoid and Solid State Relay when the output driver is off. Therefore a low AIR circuit indicates a driver is always on and a high circuit indicates an open in the PCM.

The DTC associated with this test is DTC P0412.

2. The AIR Monitor circuit is held low by the resistance path through the Air Pump when the pump is off. If the AIR Monitor circuit is high there is either an open circuit to the PCM from the pump or there is power supplied to the Air Pump. If the AIR Monitor is low when the pump is commanded on, there is either an open circuit from the SSR or the SSR has failed to supply power to the pump.

The DTCs associated with this test are DTCs P1413 and P1414.

3. The functional check may be done in two parts; at startup when the Air Pump is normally commanded on, or during a hot idle if the startup test was not able to be performed. The flow test relies upon the HO2S sensor to detect the presence of additional air in the exhaust when introduced by the Secondary Air Injection system.

The DTC associated with this test is DTC P0411.

4. The MIL is activated after one of the above tests fail on two consecutive drive cycles.