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1998 Toyota Sonoma P0404 EGR Fault: Symptoms, Diagnosis & Fixes

Model: 1998 Sonoma Fault Code: P0400 Posted: 2008-07-20 14:01

Hi everyone! I own a 1998 Toyota Sonoma with a 2.2L engine and 5-speed manual transmission. I've recently been experiencing a persistent P0404 diagnostic trouble code, which indicates an EGR (Exhaust Gas Recirculation) circuit fault. I removed the EGR valve to inspect the solenoid. Measurements showed: - Pin 1 (12V supply): 9 ohms resistance when tested between this pin and ground - Pin 2 (5V signal): open circuit — no resistance detected While the engine was running, I confirmed 12 volts on Pin 1 and 5 volts on Pin 2 using a multimeter. This confirms an electrical issue with the EGR solenoid. My truck has been exhibiting unusual behavior: - Occasional engine jerking while driving at highway speeds - A noticeable surge or power spike around 3,800 RPM when shifting gears - Fuel efficiency has dropped by approximately 2–3 MPG To rule out catalytic converter issues, I plan to use a temperature gun to measure intake and exhaust temperatures before and after the catalytic converter. However, I'm wondering if the EGR system is indeed the root cause. Any advice or suggestions on how to proceed — especially regarding EGR solenoid replacement or other potential components — would be greatly appreciated! Thanks, Steve

Related fault codes
P0400
Comments (5)
Anonymous 2008-07-20 14:35

Yes, the symptoms you're describing are very typical of an EGR system failure. This is a common issue on 1998 Toyota Sonomas with 2.2L engines.

Anonymous 2008-07-21 22:29

Double-check your readings — did any pin actually show resistance? Was the circuit truly open? If there's an open wire or connection, that should be prioritized before replacing components. Please update with your findings.

Anonymous 2008-07-28 08:01

No problem — I've been away for a while due to work. I retested the EGR solenoid: Pin 1 (12V) to ground reads 9 ohms, and Pin 2 (5V) shows an open circuit with no resistance. All other pins show only resistance on Pin 1 when tested to ground. I then applied power directly to the solenoid: - Applying 12V to Pin 1 caused the solenoid to engage properly - Applying 12V to Pin 2 resulted in no response, confirming a faulty signal or internal failure My catalytic converter was replaced about 5 years ago and at around 100k miles — could it be failing now? I also suspect another issue: I've noticed oil seeping into the airbox before the throttle body. There's a black oily film on the butterfly valve, and I can see oil running down the inside of the intake box. Any insights or recommendations would be much appreciated! Thanks, Steve

Anonymous 2008-07-28 15:25

Great follow-up — next steps: replace the EGR solenoid. This should resolve most symptoms. Regarding the oil in the intake box, while a small amount can sometimes be normal, it's often linked to a failing PCV valve. Consider checking or replacing that component as well. Please keep us updated on your progress.

Anonymous 2008-07-28 18:02

Thanks f.i.c.! I'll update you once the repairs are done.