1999 Dodge Durango 4x4 5.2L: PO132, PO135, PO141, PO720 Fault Codes & Transmission Not Shifting into High Gear

The PO720 code relates to the transmission and indicates an issue with the output speed sensor. However, PO132 and PO135 are related to oxygen sensors—specifically the upstream and downstream O2 sensors in the exhaust system. The fact that all these codes appear together may suggest a shared wiring harness problem between the transmission and oxygen sensor connectors, or a faulty ground connection.

Can PO720 alone cause the transmission to fail shifting into high gear? I've seen this behavior in several 1999 Dodge Durango models—without accurate speed input, the transmission control module cannot determine proper shift timing.

Yes, nearly all Chrysler vehicles rely on the output speed sensor to detect vehicle speed and trigger gear shifts. If this sensor is faulty or disconnected, the transmission will typically remain in second gear, risking severe internal damage if left unaddressed.

Where exactly is the output speed sensor located on a 1999 Dodge Durango? Is it mounted on top of the rear differential housing or on the driver's side of the transmission?

I found the output speed sensor—after removing the transmission skid plate, I could see it clearly. The sensor is located on the driver’s side of the transmission, near the rear differential housing. With better access, I also inspected the oxygen sensors and confirmed they were accessible. Thanks to everyone for the help—it's now fixed!

After replacing the speed sensor, my speedometer stopped working, and a yellow warning light with 'Misc. Monitor' icons is now flashing on my OBD-II system. During a test drive, I only achieved 8 MPG—why is fuel efficiency so poor?

The speed sensor issue was not fully resolved before the speedometer failed. Regarding the yellow light and flashing 'Misc. Monitor' icons on the OBD-II system, this typically indicates that the I/M (Inspection & Maintenance) monitors are not complete. Clearing codes resets these monitors, so you must go through a full drive cycle—driving under various conditions including highway speeds—to allow them to reinitialize. Some monitors require highway driving to validate; fixing the root cause first is essential.

Where did you purchase the output speed sensor for your 1999 Dodge Durango?

I bought the replacement speed sensor at AutoZone—it matches exactly with the one I removed. After installation, the transmission shifts properly and drives normally. However, my speedometer now doesn't work at all. I can’t find any information on why this would happen after replacing a speed sensor—has anyone else experienced this?