2004 Kia Optima tachometer not working... need advice

Kia Models Forum Optima
1

Hi all, I’m working on a 2004 Kia Optima 2.4L and the tachometer isn’t functioning. I’ve already replaced the crankshaft sensor, but it didn’t fix the issue. If I disconnect the cam or crank sensors, the car shuts off, so they seem to be working. I’m also getting codes P0320 and P0122, and the RPM doesn’t show up on live data with the scan tool. When I turn on the AC or shift into gear, the car feels like it’s about to stall with very low RPMs. Could this be an issue with the ECM or something else? Any help is appreciated!

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P0320 usually points to an issue with the ignition failure sensor or its wiring. Have you checked the connections there?

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Jeremybeans said:
P0320 usually points to an issue with the ignition failure sensor or its wiring. Have you checked the connections there?

Thanks for the tip! I’ll check the wiring around the ignition failure sensor and report back.

4

If the RPM isn’t showing on the scan tool, it might indicate a problem with the ECM not transmitting the signal to the tachometer. You could check the ECM connections.

5

nesh said:
If the RPM isn’t showing on the scan tool, it might indicate a problem with the ECM not transmitting the signal to the tachometer. You could check the ECM connections.

Good point! I’ll inspect the ECM connections. Do you know where the ECM is located in this model?

6

@KiaKing
It should be under the center part of the dash. Let me know if you find anything!

7

P0122 is related to the throttle position sensor. Have you checked if the sensor or its wiring is causing the low RPM issue?

8

deirdrebuttner said:
P0122 is related to the throttle position sensor. Have you checked if the sensor or its wiring is causing the low RPM issue?

I haven’t looked into that yet, but it sounds like a good idea. I’ll test the TPS and its wiring next.

9

The stalling issue when the AC is on could also be related to the idle air control valve. It’s worth checking alongside the TPS.

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rick said:
The stalling issue when the AC is on could also be related to the idle air control valve. It’s worth checking alongside the TPS.

Thanks, I’ll add that to my checklist. Hopefully, I can narrow this down soon!

11

If you’ve replaced the crankshaft sensor and the problem persists, double-check the harness and wiring for any signs of damage or corrosion.

12

Tracy said:
If you’ve replaced the crankshaft sensor and the problem persists, double-check the harness and wiring for any signs of damage or corrosion.

Will do! I’ll take a closer look at the wiring and post an update if I find anything.