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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1998 🢒 DeVille 🢒 Engine 🢒 Engine Controls - 4.0L and 4.6L 🢒 DTC P1121 Throttle Position (TP) Sensor Circuit Intermittent High Voltage

Object Number: 12985 Size: SF
Engine Controls Components
Cell 20: Engine and Fuel Tank Sensors
OBD II Symbol Description Notice
ESD Notice
ESD Notice

Circuit Description

The Throttle Position (TP) 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. DTC P1121 sets when the PCM detects a TP sensor signal that is 4.96 volts or higher which is not possible under normal operation.

Conditions for Running the DTC
    •  DTCs P0122 and P0123 not set.
    •  Engine speed between 0 and 3000 RPM.

Conditions for Setting the DTC

Throttle position 4.96 volts or greater.

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.

Diagnostic Aids

If fault is not present perform Powertrain Ground Check and also review Failure Rec. to determine conditions under which and how long ago the DTC set.

Test Description

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

  1. Checking if DTC P0120 is also set. If it is, go there first because it may help to pinpoint a faulty TP sensor.

    2.

  2. Checking for an intermittent short to voltage in the TP sensor 5 volt reference circuit or the TP sensor signal circuit that may be causing a high TP input.

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Turn the key ON.

Is DTC P0120 or P0123 also set?

--

Go to the appropriate DTC Tables

Go to Step 3

3
  1. Record the fluid life indexes, turn the key to OFF and wait 30 seconds.
  2. Disconnect PCM connector C1.
  3. Examine terminals 12, 63 and 68 of C1.
  4. Repair terminal contact if needed.

Was terminal contact repaired?

--

Go to Powertrain Control Module Diagnosis

Go to Step 4

4
  1. Disconnect Throttle Position (TP) sensor connector.
  2. Examine all TP sensor connector terminals.
  3. Repair terminal contact if needed.

Was terminal contact repaired?

--

Go to Powertrain Control Module Diagnosis

Go to Step 5

5

  1. Check the TP sensor ground circuit for possible open.
  2. Check the TP sensor 5 volt reference circuit or the TP sensor signal circuit for possible short to voltage.
  3. Repair circuit(s) if needed.

Was a repair made to any circuit?

--

Go to Powertrain Control Module Diagnosis

Go to Diagnostic Aids