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2003 Dodge Dakota P0508 and P0509 Codes: IAC Issues, Wiring Problems, or PCM Fault?

Model: 2003 Dodge Dakota Fault Code: P0508 Posted: 2014-09-02 22:43

I own a 2003 Dodge Dakota with a 4.7L engine. The truck won't start on its own but will run when the gas pedal is pressed—however, it stalls shortly after. After scanning for trouble codes, I received P0509. I inspected the wiring and idle air control (IAC) valve, which appeared normal. After clearing the code, I disconnected the IAC valve. With the IAC unconnected, the vehicle triggered P0508. My IAC only has two wires, unlike what many troubleshooting guides suggest—some claim it should have four. So I clipped the existing two wires at the powertrain control module (PCM). Now both P0508 and P0509 appear again. Am I missing two wires? Could this be a wiring issue or a faulty PCM? Any guidance would be greatly appreciated.

Related fault codes

P0508P0509

Comments (3)

Anonymous 2014-09-03 07:29

In Chrysler vehicles from 2003 and 2004, the Next Generation Controller (NGC) uses a linear idle air control motor with only two wires. Remove the IAC valve and inspect the passages for obstructions or damage to the pintle. Measure the resistance of the IAC motor—it should be approximately 9.7 ohms ±1 ohm. If outside this range, replace the IAC. Possible issues include a shorted ground in the IAC control circuit, an open or shorted signal circuit, or a faulty IAC motor. Circuit testing is recommended to confirm these faults. A defective PCM is possible but unlikely. Never clip wires—doing so can damage internal transistor drivers in the PCM. Always reconnect wires properly and avoid crossing connections.

Anonymous 2014-09-04 15:08

I replaced the IAC valve, but the P0509 code persists. I clipped the two wires after reading a reference on this site: http://www.obd-codes.com/p0505. The principle should be similar for these codes. However, when I clip the wires, the code doesn't reset—it changes to both P0508 and P0509. This makes me suspect a PCM issue. Also, when I connect the red and gray wire to the yellow and black wire at the same time (one lead on red-gray, one on yellow-black), I get a connection—this suggests possible circuit continuity or grounding issues that may point to internal faults.

Anonymous 2014-09-04 23:51

Do you have a digital multimeter? Voltage checks would be necessary to diagnose the issue accurately. As previously mentioned, resistance testing of the IAC motor is essential—ensure it reads within the correct range (9.7 ohms ±1 ohm). A faulty IAC or wiring could cause both P0508 and P0509; however, proper diagnostics with a multimeter will help confirm whether the issue lies in the sensor, circuit, or module.