All,
Just thought I'd share a tid-bit of information with the communuty on how to achieve EGR readiness while your EGR system is removed. This is particularly important in states where the OBD2 (OBDII) system is tested for readiness as a prerequisite for passing an emissions inspection.
After reading the multitudes of EGR threads here on Mud, there is a wealth of information on how to delete the EGR, and how to prevent a CEL (MIL) from occuring (P0401/P0402). However, once the ECU is disconnected from power (battery disconnected, ECU removed, etc) the OBD readiness tests will reset, and the resistor mod alone will not allow the ECU to achieve readiness. It never will, trust me, I tried every driving pattern possible and over 600 miles of driving.
The members of the forum who do have the system ready and the resistor mod in place, after investigation via PM, never disconnected their batteries. Their EGR was ready prior to removal, and once they need to achieve readiness again, they will be unable to. The other people who did the mod and cleared the code, never got ready afterwards to my or their knowledge.
I did a lot of research on trying to figure out what the ECU wants to "see" to determine that the EGR system is functioning properly, and the answer is quite simple, a significant change in EGR temp once the VSV for EGR is cycled. When the EGR is closed, it wants a cold temp, when it is open it wants a warm temp. A "warm" temp would be somewhere in the 2k ohm to 5k ohm range, and a "cold" temp would be in the 100k-200k range on the EGT temp sensor. How did I achieve this?
I put a 200k resistor in where the EGR temp sensor was, and I wired a 2k resistor in parallel with the 200k resistor. The 2k half of the circuit was wired to an automotive relay normally left open, and I used the ECU's VSV trigger to close the relay. When the ECU wants the EGR on, magically the resistance drops to a little over 2k. FWIW, one side of the VSV has constant 12V power, the ECU cycles it via a ground trigger.
My system literally went from not ready, to ready in less than 1 mile of driving, verified via my scan tool. Once readiness was achieved, I removed my relay concoction and put a 4.3k resistor in for the temp sensor, and no code since, system ready.
SEE POST BELOW FOR UPDATE!!!
There is a catch though... somehow the relay really pissed off the ECU, and I'm a mechanical engineer, not an electrical engineer, so I don't know why. My guess is that the VSV is not a true solenoid, but a variable valve that can send a varying vacuum load to the EGR valve. Since the relay is essentially an on-off switch, the ECU wasn't seeing the load it wanted at the VSV. A resistor in line may have fixed this, but like I said, I'm a ME, not an EE. At mid-throttle, the relay caused a random misfire. At low throttle the truck was fine, and at large throttle openings the truck was fine. If driven at mid throttle it would throw a misfire code, which upon reset would put the EGR back to not ready
doh. That's the whole reason for the immediate switch to the 4.3k resistor once readiness was achieved.
SEE POST BELOW FOR UPDATE!!!
I know this all sounds hokey, but it was much easier than removing my intake a second time and re-installing my EGR system just to get through inspection.
Just thought I'd share a tid-bit of information with the communuty on how to achieve EGR readiness while your EGR system is removed. This is particularly important in states where the OBD2 (OBDII) system is tested for readiness as a prerequisite for passing an emissions inspection.
After reading the multitudes of EGR threads here on Mud, there is a wealth of information on how to delete the EGR, and how to prevent a CEL (MIL) from occuring (P0401/P0402). However, once the ECU is disconnected from power (battery disconnected, ECU removed, etc) the OBD readiness tests will reset, and the resistor mod alone will not allow the ECU to achieve readiness. It never will, trust me, I tried every driving pattern possible and over 600 miles of driving.
The members of the forum who do have the system ready and the resistor mod in place, after investigation via PM, never disconnected their batteries. Their EGR was ready prior to removal, and once they need to achieve readiness again, they will be unable to. The other people who did the mod and cleared the code, never got ready afterwards to my or their knowledge.
I did a lot of research on trying to figure out what the ECU wants to "see" to determine that the EGR system is functioning properly, and the answer is quite simple, a significant change in EGR temp once the VSV for EGR is cycled. When the EGR is closed, it wants a cold temp, when it is open it wants a warm temp. A "warm" temp would be somewhere in the 2k ohm to 5k ohm range, and a "cold" temp would be in the 100k-200k range on the EGT temp sensor. How did I achieve this?
I put a 200k resistor in where the EGR temp sensor was, and I wired a 2k resistor in parallel with the 200k resistor. The 2k half of the circuit was wired to an automotive relay normally left open, and I used the ECU's VSV trigger to close the relay. When the ECU wants the EGR on, magically the resistance drops to a little over 2k. FWIW, one side of the VSV has constant 12V power, the ECU cycles it via a ground trigger.
My system literally went from not ready, to ready in less than 1 mile of driving, verified via my scan tool. Once readiness was achieved, I removed my relay concoction and put a 4.3k resistor in for the temp sensor, and no code since, system ready.
SEE POST BELOW FOR UPDATE!!!
There is a catch though... somehow the relay really pissed off the ECU, and I'm a mechanical engineer, not an electrical engineer, so I don't know why. My guess is that the VSV is not a true solenoid, but a variable valve that can send a varying vacuum load to the EGR valve. Since the relay is essentially an on-off switch, the ECU wasn't seeing the load it wanted at the VSV. A resistor in line may have fixed this, but like I said, I'm a ME, not an EE. At mid-throttle, the relay caused a random misfire. At low throttle the truck was fine, and at large throttle openings the truck was fine. If driven at mid throttle it would throw a misfire code, which upon reset would put the EGR back to not ready
doh. That's the whole reason for the immediate switch to the 4.3k resistor once readiness was achieved.SEE POST BELOW FOR UPDATE!!!
I know this all sounds hokey, but it was much easier than removing my intake a second time and re-installing my EGR system just to get through inspection.
Last edited:
