Nissan Altima: Trouble codes P1122 and P1128

Nissan Altima has Trouble codes P1122 and P1128. The trouble code P1122 is a Electric Throttle Control Function code, and the P1128 is a Throttle Control Motor (TCM) code.

The original concern on this Nissan Altima was that the throttle does not respond. Along with the codes, we were certain that Some simple diagnostic procedures would send us to the culprit. Here is a list of the first test procedures that were performed on this Altima. But, after being in the automotive industry for more than 25 years, we know that things are not always as it seems. The codes P1122 and P1128 are just a starting point, it will be up to the tech to find out the acual cause of the code being set. Be aware that the customer went to autozone and had the codes read, they suggested that it was the throttle control actuator, and 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.

Trouble codes P1122 and P1128 are the codes present

Diagnostic Procedure:

CHECK:

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

OK: proceed to 10 NG: 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.

OK: proceed to 8 NG: 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 20A

OK: proceed to 9 NG: replace the fuse

9. Intermittent incident

Refer to Trouble Diagnosis for Intermittent Incident

OK: replace IPDM E/R NG: 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 TER ECM TER CONTINUITY

3 5 no

4 yes

6 5 yes

4 no

Harness for short to ground / power.

OK: proceed to 11 NG: repair / replace.

11. Visually inspect actuator.

Take the intake air duct out

Look for dirt grease etc. in the valve and housing.

OK: proceed to 12 NG: clean the inside of the actuator.

12. Inspect motor.

OK: proceed to 13 NG: 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 O at 25°C 0r 77°F

NG: 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.

Ok, lets do a quick recap:

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

MILEAGE: 218168

Customer Concern: Throttle doesn't respond. Trouble codes P1122 and P1128 present. Replaced the throttle control actuator.

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

Tests:

1. Check the resistance of the throttle control motor. 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: Repaired Engine Control Module (ECM) Ground(s)

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.