GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1996 🢒 Seville 🢒 DTC 🢒 DTC P0120 TP System Performance

Object Number: 12985 Size: SF
Engine Controls Components
IAT/ ECT/ TP/ MAP and BBV Sensors
OBD II Symbol Description Notice
ESD Notice
ESD Notice

Circuit Description

The Throttle Position sensor is potentiometer. A 5 volt reference is provided on CKT 605 and ground is provided on CKT 808. The TP sensor signal CKT 417 varies between ground and 5 volts based on the position of the throttle plates. At low throttle angle, the TP sensor signal voltage is low. The PCM uses TP sensor information to determine idle, Wide Open Throttle (WOT), deceleration enleanment and acceleration enrichment. This diagnostic test monitors both the Manifold Absolute Pressure (MAP) and Throttle Position (TP) sensors. Engine operation requires that any large change in throttle position (TP) sensor must be followed by a change in manifold pressure (MAP). If the MAP remains constant following a large change in throttle angle, PCM DTC P0120 will set.

Conditions for Setting the DTC

Test Conditions

    • DTCs P0107, and P0108 not set.
    • MAP greater than 21.8 kPa.
    • MAP not within 12 kPa of atmospheric pressure (BARO).
    • Engine speed at least 500 RPM.
    • Engine metal overtemp not active.
    • Traction control not active.

Failure Conditions

MAP signal changes 3 kPa or less in 0.21 seconds following a 5 degree or greater INCREASE in throttle angle.

OR

MAP signal changes 2.2 kPa or less in 0.21 seconds following a 4.7 degree or greater DECREASE in throttle angle.

Action Taken When the DTC Sets

    •  The Malfunction Indicator Lamp (MIL) will not illuminate.
    •  No message will be displayed.

Conditions for Clearing the DTC

    •  A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.
    •  A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
    • Use a scan tool to clear DTCs.
    • Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

  1. Since a misfire can cause DTC P0120 to set, if a misfire has occurred, it should be diagnosed first.

    2.

  2. Checking DTC P0120 snapshot value to determine if an intermittent low voltage caused the DTC to set.

    3.

  3. An intermittent low voltage can be caused by an open or short to ground on the TP sensor circuit or by an open in the TP sensor 5volt reference circuit or the TP sensor itself.

    4.

  4. Checking the TP sensors ability to react to a known throttle angle.

    5.

  5. Checking DTC P0120 snapshot value to determine if an intermittent high voltage caused the DTC to set.

    6.

  6. An intermittent high voltage can be caused by an open in the TP sensor ground circuit or a short to voltage on the TP sensor signal circuit.

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to A Powertrain On Board Diagnostic (OBD) System Check

2

  1. Connect a scan tool.
  2. Turn the key ON

Is DTC P0300 also set?

--

Go to DTC P0300 Engine Misfire Detected

Go to Step 3

3

Are DTCs P0121 or P0122 set?

--

Go to DTCs that are set

Go to Step 4

4

Select Failure Rec. and view TP sensor display.

Is snapshot TP sensor reading less than the value specified?

0 degrees

Go to Step 5

Go to Step 8

5

  1. An intermittent low voltage reading occurred on the TP sensor circuit.
  2. Look for a possible open or short to ground on the TP sensor signal circuit and for a possible open on the TP sensor 5 volt reference circuit.
  3. Repair the open or shorted condition if found.

Was an open or shorted condition repaired?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

Go to Step 6

6

  1. Check TP sensor reading as you SLOWLY depress the accelerator from closed throttle to wide open throttle.
  2. Watch for a skip or jump in the TP sensor reading.

Was a skip or jump in TP sensor reading noted?

--

Go to Step 7

Fault not present.

7
  1. Check for the following conditions:
    2. • Sticky or binding throttle.
    • Wiring chaffed or binding on the throttle.
  2. Repair either condition if found.

Was a repair made?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

Go to Step 11

8

Is snapshot TP sensor reading greater than the value specified?

85 degrees

Go to Step 9

Go to Step 6

9

  1. An intermittent high voltage reading occurred on the TP sensor circuit.
  2. Look for a possible open on the TP sensor ground circuit and for a possible short to voltage on the TP sensor signal circuit.
  3. Repair the open or shorted condition if found.

Was an open or shorted condition repaired?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

Go to Step 10

10
  1. Check TP sensor reading as you SLOWLY depress the accelerator from closed throttle to wide open throttle.
  2. Watch for a skip or jump in the TP sensor reading.

Was a skip or jump in TP sensor reading noted?

--

Go to Step 11

Fault not present. Refer to Diagnostic Aids

11

Replace the Throttle Position sensor. Refer to TP Sensor Replacement .

Is the replacement complete?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

--