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Isuzu Axiom 2003 Check Engine Light & Codes P1125, P1221, P1295, P1515: Throttle Sensor or Wiring Issue?

Model: Isuzu Axiom Fault Code: P1125 Posted: 2009-01-31 10:54

I own a 2003 Isuzu Axiom SUV and have been experiencing intermittent engine stalling and poor performance for years. Despite multiple repairs—including intake manifold gaskets (three replacements in five years), head gaskets, catalytic converter, PCV valve, fuel filter, air filter, and fuel injector cleaning—the issue persists. A month ago, I had a new intake manifold gasket installed at a dealership on Harlem and I-55. The day after driving it home, the engine ran poorly. Now, 45 days later, the vehicle stalls frequently, and both the check engine and reduced power lights are illuminated. The OBD2 diagnostic codes reading are P1125, P1221, P1295, and P1515. The dealership claims these codes point to a faulty wiring harness costing $1,500 and states they cannot guarantee the fix will resolve the issue. I’ve spent over $2,000 in the past six months on repairs for the same symptoms, and I’m increasingly concerned that dealerships are diagnosing incorrectly—just reading codes without addressing root causes. As a single vehicle owner with limited public transportation access, especially during cold weather (currently 15°F), this issue is not just mechanical—it’s life-critical. I’d like to know if the diagnosis of these specific Isuzu Axiom 2003 codes is accurate and whether there are more cost-effective or reliable solutions than a $1,500 wiring harness replacement. TIA!

Related fault codes
P1125P1221P1295P1515
Comments (5)
Anonymous 2009-01-31 14:25

The P1125, P1221, P1295, and P1515 codes on an Isuzu Axiom 2003 are primarily related to the throttle position sensor (TPS) in the throttle body assembly. Has the dealership inspected or serviced the throttle body itself? This is a key component that may be causing the erratic engine behavior.

Anonymous 2009-01-31 15:02

I’ve reviewed the work history: intake manifold gaskets, head gasket, catalytic converter, PCV valve, new fuel filter, new air filter, and fuel injector cleaning. The codes are: - P1125: Isuzu – Electronic Throttle Control (ETC) Limit Performance Mode - P1221: Isuzu – Throttle Position Sensor 1/2 Circuit Performance Issue - P1295: Isuzu – ETC Power Management Mode - P1515: Isuzu – TP Sensor to MAF Sensor Correlation Error Are there any accessible checks I can perform on the vehicle? For example, inspecting connections or wiring related to the throttle body and TPS sensors?

Anonymous 2009-01-31 15:16

The throttle position sensor is located inside the throttle body and is difficult to test without specialized equipment. However, ensuring all electrical connectors are securely plugged in and free of corrosion is a basic but important step.

Anonymous 2009-03-16 17:25

Hi—I just joined this forum after reading your post last week. I brought my 2002 Isuzu Rodeo to the dealer with similar symptoms: random check engine light, stalling, and poor performance. The mechanic initially said it was a head gasket leak into a spark plug tube, but later discovered the issue was actually external—cracked engine wiring harness causing intermittent signals. After replacing the wiring harness, they found a cracked cylinder head and replaced both components. Now my vehicle runs smoothly with no check engine light. The total cost was $1,600 (head gaskets, harness, labor, plus oil change). I live in Maine and this experience helped me avoid further costly repairs. I hope your issue is resolved through similar diagnostics—especially since the codes match exactly. Good luck!

Anonymous 2012-09-12 07:04

I have a 2003 Isuzu Axiom with the check engine and reduced power lights on, and the vehicle runs slowly. The codes match those reported by surfsup. However, most of these issues were cleared electronically—yet the reduced power and check engine lights remain active. The mechanic suspects that one side of the V6 engine lacks power, possibly due to a faulty ETC (Electronic Throttle Control) power supply or ECU issue. Any advice on how to verify this or what steps to take next would be greatly appreciated.