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Nissan Altima: Trouble Codes P1122 and P1128

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After being in the automotive industry for more than 25 years, we're adept at helping people with their car troubles.

Our Problem: Throttle Won't Respond in a 2002 Nissan Altima

From our notes:

Vehicle: 2002 Nissan Altima SE 3.5L, V6, MFI, DOHC, Eng Desg VQ35DE, 3498 CC

Mileage: 218168

Customer concern: Throttle doesn't respond. Trouble codes P1122 and P1128 present. Customer replaced the throttle control actuator, which didn't solve the problem.

Nissan Altima Trouble Codes P1122 and P1128

We were presented with a Nissan Altima whose throttle didn't respond. It showed trouble codes P1122 and P1128. If you look them up, trouble code P1122 is an Electric Throttle Control Function code, and the P1128 is a Throttle Control Motor (TCM) code.

We were certain that the codes plus some simple diagnostic procedures would send us to the culprit. But, after being in the automotive industry for more than 25 years, we know that things are not always as they seem. The codes P1122 and P1128 are just a starting point; it will be up to the tech to find out the actual cause of the code being set.

When the customer went to Autozone and had the codes read, they suggested that it was the throttle control actuator, so the customer decided to order the part from the Nissan dealership and install it himself. Needless to say, this did not fix his vehicle. Read on to learn what we found and how we repaired this Nissan Altima.

Nissan Altima throttle actuator plug

Nissan Altima throttle actuator plug

What We Checked in This Diagnostic Procedure

Here is a list of the first test procedures we did on this Altima. You can find this list in many places on the web.

1. Ground screws

  • Switch off ignition.
  • Loosen and tighten the body screws.

2. Motor relay signal circuit I

  • Between ground and ECM terminal 3, check the voltage as given:

Ignition switch off: 0V

Ignition switch on: 11 – 14V

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  • If OK: proceed to 10, if no good: proceed to 3

3. Motor relay input signal circuit II

  • Switch off ignition
  • Disconnect the harness connector to the ECM
  • Disconnect the harness connector E 14 of IPDM E/R.
  • Between ECM terminal 3 and IPDM E/R terminal 28:-harness continuity. Continuity should be there.

Harness for short to ground/power.

4. Part that is malfunctioning

  • Harness connectors E50, F1.
  • Harness connector E14 of IPDM E/R.
  • Harness for open/short between ECM and IPDM E/R

Repair open / short to ground / power in harness / connectors.

5. Motor relay power supply circuit I

  • Connect all the harness connectors.
  • Switch off ignition
  • Between ground and ECM terminal 104 check the voltage (battery).

6. Motor relay power supply circuit.

  • Disconnect the harness connector to the ECM.
  • Disconnect the harness connector E17 of IPDM E/R
  • Between ECM terminal 104 and IPDM E/R terminal 70 check for continuity (there should be continuity).
  • Harness for short to ground/power.

If OK: proceed to 8. If no good: proceed to 7

7. Find the malfunctioning part. Check:

  • IPDM E/R harness connector E17.
  • Between ECM and IPDM E/R harness for open/short.
  • Repair open / short to ground / power in harness / connectors.

8. Fuse

  • Disconnect the fuse (20A)
  • Check for a blown fuse

If OK: proceed to 9. If no good: replace the fuse

9. Intermittent incident

Refer to Trouble Diagnosis for Intermittent Incident

If OK: replace IPDM E/R. If no good: repair/replace harness/connectors.

10. For open/short in motor output signal circuit

  • Switch off ignition.
  • Disconnect the harness connector to the actuator.
  • Disconnect the harness connector to the ECM.
  • Check for harness continuity between terminals.
Actuator terminalECM TerminalContinuity?











Harness for short to ground/power.

If OK: proceed to 11. If no good: repair / replace.

11. Visually inspect actuator.

  • Take the intake air duct out
  • Look for dirt, grease, etc. in the valve and housing.

If OK: proceed to 12. If no good: clean the inside of the actuator.

12. Inspect motor

If OK: proceed to 13. If no good: proceed to 14

13. Intermittent Incident

Refer to Trouble Diagnosis for Intermittent Incident.

14. Replace the Actuator

End of Inspection

Component Inspection

Disconnect the harness connector to the actuator.

Between terminals 3 & 6 check the resistance: approx. 1 – 15 Ω at 25°C or 77°F.

If no good: replace and proceed to next step.

Remember that the customer already replaced the throttle control actuator himself, in hopes of a simple fix. But we still have to follow the diagnostic procedures in order for us to be as thorough as possible.

More Tests We Did

After performing the standard diagnostic tests above, one of my techs decided to go a different route. This is the procedure he performed.


1. Check the resistance of the throttle control motor. The specification is 1 to 15 ohms at 77 degrees °F (a known good resistance value is around 8 ohms).

2. Check the circuit between the Electronic Control Module (ECM) and the throttle control motor. Disconnect the throttle control motor and the ECM. Wire a headlight bulb to the blue/black and blue/white wires at the throttle control motor connector. Locate pins 5 (blue/black) and 4 (blue/white) at the ECM connector, then apply battery voltage to one wire and a ground on the other. Check the headlight bulb. The headlight bulb will flow about 4 amps through the circuit. If the bulb lights and is bright, wiggle-test the harness.

3. Voltage-drop the powers and grounds at the ECM. Also voltage-drop the orange wire at pin 3 of the ECM connector (everything connected and backprobing).

Potential Causes:

(A) Electronic Control Module (ECM)

(B) Throttle Motor Control Relay

(C) Wiring is corroded

Confirmed Fix

We repaired the Engine Control Module (ECM) grounds, and that fixed the customer's problem.

Tech Tips

Trouble code P1128 is set when the ECM detects a shorted throttle control motor circuit or the throttle control motor is shorted. The P1122 is typically set when the throttle control function does not operate properly. It is common to see the throttle control motor supply voltage low due to a poor throttle motor relay. The ECM receives this voltage from the relay and distributes it to the throttle motor.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

© 2010 Gefforyt

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