P0123 Code on 1999 Jeep Wrangler Sport: TPS Replacement Failed - Sputtering & CE Light Issues

Inspect the wiring harness leading to the TPS for signs of wear, chafing, or damage. If no visible issues are found, use a multimeter or oscilloscope to test the TPS signal wire — look for an open circuit, short to power, or ground fault. These are common causes of P0123 codes.

I strongly recommend scoping the TPS signal directly if the power and ground circuits are intact. A faulty clock spring can indeed cause false TPS readings in certain Jeep models, especially due to how the 5-volt reference is wired. To confirm this: disconnect the clockspring and re-scan for P0123. If the code disappears, it's likely the root cause. This issue is well-documented on forums like IATN — particularly in older Chryslers and Jeeps. As a practical step, try replacing the PCM, harness, and MAP sensor first; if that doesn’t resolve it, then focus on the clockspring. Also, scan for airbag faults — they’re often linked to the same electrical interference.

I'm confused about how a clock spring could affect the TPS signal. The TPS and airbag systems appear unrelated. The P0123 code is tied directly to throttle position, while the CE light relates to airbag module faults. Can someone explain the technical connection between these two components? I’ve heard the clockspring mentioned several times but no one has clarified how it could interfere with TPS operation.

Yes, you're on this forum too — it's tough to piece together without clear technical explanations. The airbag and TPS systems are separate, so their interaction is not immediately obvious.

The clockspring has no direct impact on the TPS signal. The P0123 code relates to throttle position — a sensor issue or wiring fault. The CE light indicates an airbag module problem, which is unrelated. These are two distinct systems. If you're seeing both, it suggests separate faults, not a shared root cause.

In some cases — especially on Chrysler and Jeep platforms like the 1999 Wrangler — a failing clock spring can interfere with the TPS circuit due to electrical noise in the 5-volt reference line. This interference can mimic a faulty TPS, even after replacement. I’ve personally seen this on multiple vehicles: 1999 Caravan, 2002 Cherokee, and several Dakota models. Clocksprings often cause intermittent faults that worsen with steering movement. A simple test is to disconnect the clockspring — if the P0123 code vanishes and performance improves, it's likely the culprit. I recommend this as a quick diagnostic step before replacing expensive components like the PCM or MAP sensor.

I’ve confirmed that in my case, disconnecting the clockspring resolved both the sputtering and the P0123 code. The airbag light also went off after the fix. While the check engine light initially cleared, I suspect it may return under certain conditions. This experience aligns with several reported cases on this forum — especially when the airbag light is present.

That makes sense — the diagnosis should start with the TPS and then move to the clockspring if symptoms persist. The wiring diagrams for these systems are complex, and the connection between them isn’t immediately obvious, but it does exist in certain vehicle architectures.

The key is understanding the internal wiring — especially how the 5-volt reference signal from the clockspring can interfere with TPS readings. This issue is not intuitive, but it’s well-documented. I’ve seen it on multiple vehicles where steering movement causes intermittent faults in throttle response and emissions systems. A real-world test: try moving the steering wheel back and forth while monitoring the TPS signal — if the code fluctuates or disappears, that's a strong indicator of clockspring interference.

I can confirm this is the actual root cause. In my 1998 Jeep Wrangler, the vehicle exhibited severe hesitation and misfires. After pulling diagnostic codes, I found P0123. I removed the steering column covers and disconnected the clockspring — after that, the vehicle ran smoothly with no issues or error codes. This is a proven fix for this specific model.

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My Jeep showed a P0122 code initially, which I resolved by replacing the TPS. The next day, the code changed to P0123. Could this be due to a wiring issue with the new TPS or a faulty connection in the harness? Why would replacing one sensor trigger a different fault code? Any insights on how this sequence might happen?

Have you read this entire thread? The original poster had P0123 — your case started with P0122, then shifted to P0123 after TPS replacement. This pattern may indicate a wiring or reference issue rather than a genuine sensor failure.

I’ve read the thread thoroughly. The original poster had P0123, and I started with P0122 — after replacing the TPS, I now get P0123. This suggests that either the new TPS has a wiring fault or the reference circuit is compromised. It’s possible the replacement introduced an error in the signal path.

A loose connector or damaged harness could be responsible — try disconnecting the clockspring and test driving to see if the P0123 code returns. If it does not, that strongly points to a mechanical or electrical interference issue originating in the steering column.