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2000 Jeep Grand Cherokee P0138 Check Engine Light: Diagnosis and ABS Code Issues

Model: 2000 Jeep Grand Cherokee Fault Code: P0138 Posted: 2014-09-01 16:48

My 2000 Jeep Grand Cherokee with a 4.0L engine has the check engine light illuminated. I took it to AutoZone for an OBD2 scan, which returned code P0138. The technician also mentioned that several ABS-related codes were detected—specifically 2, 4, 8, 9, and 12. I filled up with gas and drove around the neighborhood, after which the check engine light turned off temporarily. However, I'm concerned about the underlying cause since AutoZone's scanner only reads generic OBD2 codes and does not detect ABS-specific faults. The P0138 code relates to the oxygen sensor circuit in Bank 1, Sensor 2 (post-catalyst), and may indicate a faulty sensor or wiring issue. I'd like to understand how to properly diagnose this problem and whether the ABS codes are related or independent of the check engine light. A full drive cycle is recommended to trigger any pending faults and confirm if the issue returns.

Related fault codes
P0138
Comments (6)
Anonymous 2014-09-02 14:21

What were the exact ABS codes? If your scanner only detected generic OBD2 codes (like P0001–P0999), it likely doesn't support ABS diagnostics. For accurate readings, consider using a professional scan tool that can interpret both OBD2 and ABS fault codes. Perform a drive cycle to re-trigger any stored faults—this may help identify whether the issue persists or resolves on its own. More details about the code P0138 are available here: http://www.obd-codes.com/p013-8

Anonymous 2014-09-02 20:57

The ABS codes detected were 2, 4, 8, 9, and 12. These may indicate issues with wheel speed sensors or related components in the braking system.

Anonymous 2014-09-03 07:33

AutoZone's standard OBD2 scanners only read generic P-codes (e.g., P0001–P0999) and do not detect ABS-specific faults. If you're seeing ABS codes, a more advanced diagnostic tool is needed to interpret them properly. The check engine light may be triggered by either the oxygen sensor issue (P0138) or an underlying ABS fault.

Anonymous 2014-09-04 01:30

I have a 2000 Jeep Grand Cherokee with a 4.0L engine. The check engine light came on, and I took it to AutoZone for testing. They reported P0138 and said they found multiple ABS codes. After refueling and driving around, the check engine light went off temporarily. I'm unsure whether this is a sensor issue or related to the braking system.

Anonymous 2014-09-05 15:00

The check engine light came on—no other warning lights were reported at that time.

Anonymous 2014-09-05 15:06

If the check engine light is currently ON, perform a full diagnostic scan to retrieve all stored codes. Be sure to include details such as when the light first appeared, any symptoms (e.g., poor fuel economy), and whether it returns after driving. Adding more context will help identify root causes and guide proper troubleshooting.