← Back to list

2006 Nissan Titan P2138 Code: Throttle Pedal Position Sensor Voltage Correlation Fix & Diagnosis

Model: 2006 Nissan Titan Fault Code: P2138 Posted: 2017-09-01 02:04

I own a 2006 Nissan Titan with 128,000 miles. Recently, the vehicle has triggered a P2138 diagnostic trouble code, indicating a voltage correlation issue between the throttle pedal positioning sensor and the engine control module (ECM). I replaced the throttle body, but the problem persists. After hitting a pothole, the check engine light activated, confirming the P2138 fault. My mechanic suspects a faulty wiring connection, though no clear diagnosis has been made so far. The issue appears to be related to sensor signal integrity or electrical continuity between the accelerator pedal and ECM.

Related fault codes
P2138
Comments (18)
Anonymous 2017-09-01 07:09

Check the freeze frame data for any voltage spikes or inconsistencies. Verify APS1 and APS2 signals—look for open circuits, ground faults, or short-to-voltage issues. Refer to OBD-Codes for detailed sensor wiring diagrams.

Anonymous 2017-09-01 08:29

Thank you for the insight—I appreciate it.

Anonymous 2017-09-22 19:15

After weeks of troubleshooting with multiple mechanics and even a dealership, I replaced three different accelerator pedals, twice the throttle body, and installed a new ECM. The issue was ultimately traced to a crankshaft position sensor fault—something I had suspected earlier.

Anonymous 2017-09-24 10:13

Still experiencing the same P2138 code after replacing two accelerator pedals, three throttle bodies, and installing a new ECU. The dealer suggested checking spark plugs as a next step, but that doesn’t seem related to the pedal sensor voltage issue.

Anonymous 2017-09-30 17:35

Yesterday I replaced the engine room harness and performed a compression test on cylinder 4—where I was seeing a P0304 code. The result showed low compression at cylinder 4 (145 psi) compared to the other cylinders (175 psi). This suggests a potential valve issue, though it's unclear if this directly affects the P2138 code.

Anonymous 2017-10-05 12:22

After replacing the engine room harness, I discovered that cylinder 4 was not communicating with the ECM—there was a hot ground. Once fixed, the truck runs smoothly now.

Anonymous 2018-03-19 16:56

Thanks for sharing your experience! I have a 2006 Nissan Xterra showing the same P2138 code. I’ve replaced the accelerator assembly, throttle body, and ECU relay—even though my VIN wasn’t on any recall list. Could you provide more details about what the 'engine room harness' is? It sounds like a major component—would it be the engine bay wiring harness or something else? Also, should I consider replacing the IDPM (Intake Door Position Module) given its cost and relevance to pedal sensing?

Anonymous 2018-03-19 20:58

Engine room harness is likely a misstatement—it should be referred to as the engine bay wiring harness or engine loom harness. This is the main electrical bundle running from the engine to the ECM.

Anonymous 2018-03-19 21:33

Thanks for the clarification. While replacing an entire electrical harness may seem excessive, resolving the issue is more important than cost. Once the root cause is found, it's worth investing in a proper fix.

Anonymous 2018-03-20 04:49

More diagnostic testing is needed. Do you have an OBD2 scanner to monitor live data? The problem could stem from wiring issues in either the accelerator pedal or throttle body sensor circuit.

Anonymous 2018-03-20 08:31

Please help—my friend recently faced the same P2138 code and replaced the entire vehicle wiring harness. Another user also reported fixing their issue by replacing the engine loom harness. What steps should I take? Any recommendations for troubleshooting?

Anonymous 2018-03-21 07:49

I found the root cause: a pinched wire located behind the emergency brake panel on the driver’s side.

Anonymous 2018-03-21 08:16

Bro, I also have a pinched wire. However, after checking nearly every wire, my ASE-certified mechanic concluded that the ECU is faulty and recommended replacing it. Can anyone confirm if this is a common issue or if there’s a simpler fix?

Anonymous 2018-03-21 08:22

I replaced the ECU—no improvement. I also changed the engine room harness, throttle body, and accelerator pedal sensors. The actual fault was a pinched wiring harness behind the emergency brake panel. The truck had been involved in an accident, and this wire was damaged during impact. Removing the plastic panel revealed the issue.

Anonymous 2018-03-21 10:37

Hi bro—could you please describe where exactly the faulty cable is located? Is it inside the engine compartment or cabin? How did your mechanic locate it? I'm from India and would like to see a screenshot. My WhatsApp number is +919417580303. Any help would be greatly appreciated!

Anonymous 2018-03-28 10:36

atip wrote: Tue Mar 20, 2018 4:49 am Hello. More testing needed. Do you have scanner to watch live data? Could be wiring issue for Accelerator Pedal or Throttle Body. Thanks atip—I do have an OBD reader with a Pro app. Could you specify which sensor or parameter I should monitor in real-time to detect the fault?

Anonymous 2018-03-28 15:22

xitizsanjay wrote: Wed Mar 21, 2018 10:37 am Hi bro—please tell me where that faulty cable is fitted (engine compartment or cabin), how your mechanic found it, and what country you're from. I'd like to see a screenshot via WhatsApp (+919417580303). Thanks! I might be wrong, but the ECM location in my 2006 model differs from earlier generations—it's now located near the driver’s side exterior panel instead of under the center dash. This makes sense for why a wire behind the emergency brake panel would affect signal routing. I'm just a novice DIYer—apologies if this is inaccurate.

Anonymous 2018-03-29 06:43

Thanks a lot! I’ll now search for the fault using your guidance. My truck is running fine now, and I appreciate the detailed input!