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2003 Isuzu Rodeo P0155, P0004, and P4800 Code Explanation and Diagnosis

Model: 2003 Isuzu Rodeo Fault Code: P0004 Posted: 2007-05-09 17:08

The check engine light came on in my 2003 Isuzu Rodeo, but I haven't noticed any drivability issues. I recently tested the vehicle with a cheap generic OBD-II scanner I previously used on a Ford—this time, it displayed three codes: P0155, P0004, and P4800. My scanner only has four-digit display capability, so I couldn't distinguish between P-codes and other types of codes. P0155 (O2 sensor heater circuit malfunction) is listed in the owner's manual, but I'd appreciate any additional insights on how to diagnose or fix this issue. However, I'm unable to find reliable information about what P0004 and P4800 mean—especially since these codes are not commonly discussed for the 2003 Isuzu Rodeo with a 3.2L V6 engine and automatic transmission. I suspect my scanner may not be reading the serial data correctly, as it's an older model with limited protocol support. I'm considering getting a new OBD-II reader from AutoZone for verification. Can anyone confirm what these codes indicate or suggest next steps?

Related fault codes
P0004P0155P0480
Comments (6)
Anonymous 2007-05-09 17:14

More specific details: This is a 2003 Isuzu Rodeo with the 3.2L V6 engine and automatic transmission. Any additional info on the symptoms or mileage would help clarify the issue.

Anonymous 2007-05-09 17:18

Try using a different OBD-II scanner—your current device may not support the proper communication protocol for your Isuzu Rodeo. AutoZone offers free diagnostic reads; it's worth visiting to confirm the codes and get accurate readings.

Anonymous 2007-05-10 09:52

Thanks for the reply—I agree, it’s possible my scanner isn’t fully compatible with the vehicle’s protocol. It has a 'Made in China' stamp, so that might explain its limited functionality. I’ve already located AutoZone nearby and will get a second opinion from their technician. Appreciate the suggestion!

Anonymous 2007-06-14 07:57

I finally took it to AutoZone, and their scanner confirmed P0155. Now I’m trying to figure out which O2 sensor is 'Bank 2, Sensor 1' on a 2003 Isuzu Rodeo with the 3.2L V6 engine. Also, does a 'heater circuit malfunction' typically point to a faulty oxygen sensor, assuming wiring and connectors are intact?

Anonymous 2007-06-14 08:00

Bank 2, Sensor 1 refers to the oxygen sensor located on the side of the engine containing cylinder #2, specifically the front sensor before the catalytic converter. If there are no visible issues with wiring or connectors, a heater circuit failure in the O2 sensor is most likely due to an internal short or open circuit within the sensor itself.

Anonymous 2007-06-14 08:01

Just a quick tip: If you're unsure which bank corresponds to which cylinder, consider replacing both front oxygen sensors (pre-catalytic converter) on the 2003 Isuzu Rodeo. This proactive approach can save time and avoid repeated troubleshooting.