The Throttle Position (TP) sensor circuit provides a voltage signal that changes relative to throttle blade angle. The TP sensor sends a voltage signal back to the Engine Control Module (ECM) relative to the throttle plate opening. The voltage signal will vary from approximately 0.33 volts at closed throttle, to over 4.3 volts at Wide Open Throttle (WOT).

The TP signal is used by the ECM for fuel control and for most of the ECM controlled outputs. The TP signal is one of the most important inputs used by the ECM for fuel control and most of the ECM controlled outputs. If the ECM detects a TP signal that is intermittently above the range of the TP sensor, Diagnostic Trouble Code (DTC) P1121 will be set.

Check for the following conditions:

If DTC P1121 cannot be duplicated, reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

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

The Throttle Position (TP) sensor circuit provides a voltage signal that changes relative to throttle blade angle. The TP sensor sends a voltage signal back to the Engine Control Module (ECM) relative to the throttle plate opening. The voltage signal will vary from approximately 0.33 volts at closed throttle, to over 4.3 volts at Wide Open Throttle (WOT).

The TP signal is used by the ECM for fuel control and for most of the ECM controlled outputs. The TP signal is one of the most important inputs used by the ECM for fuel control and most of the ECM controlled outputs. If the ECM detects a TP signal that is intermittently above the range of the TP sensor, Diagnostic Trouble Code (DTC) P1122 will be set.

Check for the following conditions:

If DTC P1122 cannot be duplicated, reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

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

The Engine Control Module (ECM) continuously monitors the Front Heated Oxygen Sensor (HO2S1) activity for 100 seconds. During the monitor period, the ECM counts the number of times that the HO2S1 switches from rich to lean and from lean to rich. With this information, a total for all switches can be determined. If the number of switches is too low, a Diagnostic Trouble code (DTC) P1133 will set. The lean-to-rich and rich-to-lean are less than 15 switches.

DTC P1133 is most likely caused by one of the following items:

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

The Engine Control Module (ECM) monitors the Front Heated Oxygen Sensor (HO2S1) activity for 100 seconds after closed loop and stoichiometric operation have been established. During the monitoring period the ECM counts the number of times that the HO2S1 responds from rich to lean and adds the amount of time it took to complete all transitions. With this information, an average time for all transitions can be determined. The ECM then divides the -to-lean average by the lean-to-rich average to obtain the ratio. If the HO2S1 transition time ratio is not within the range, Diagnostic Trouble Code (DTC) P1134 will be set, indicating that the HO2S1 is not responding as expected to changes in exhaust oxygen content.

A malfunction in the HO2S1 ignition feed or ground circuit may cause a DTC P1134 to set. Check HO2S1 circuitry for intermittent faults or poor connections. If connections and wiring are OK and DTC P1134 continues to set, replace the HO2S1.

Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how open the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

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

The Engine Control Module (ECM) supplies a voltage of about 0.45 volts between terminals M12 and M29 (if measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volts). The Front Heated Oxygen Sensor (HO2S1) varies the voltage within a range of about 1 volt if the exhaust is rich, down through about 0.10 volts if the exhaust is lean.

In internal circuitry of the Engine control Module (ECM) can identify if the vehicle fuel system is capable of cutoff amount of the fuel supply during deceleration. When a Decel Fuel Cutoff (DFCO) mode of operation is requested during Closed Loop operation, the ECM will cutoff the fuel supply to the engine. Under these conditions the ECM should detect a lean condition. If the ECM detect a rich condition at this time, Diagnostic Trouble Code (DTC) P1167 will set. Damaged fuel pressure regulator and faulty injector will be the cause of this DTC.

The DTC P1167 or rich exhaust is most likely caused by one of the following items:

The internal circuitry of the Engine control Module (ECM) can identify if the vehicle fuel system is capable of supplying adequate amounts of fuel during heavy acceleration( power enrichment). When a Power Enrichment (PE) mode of operation is requested by heavy acceleration during Closed Loop operation, the ECM will provide more fuel to the engine. Under these conditions the ECM should detect a rich condition. If this reich condition is nor detected at this time, Diagnostic Trouble Code (DTC) P1171 will set. A plugged fuel filter or restricted fuel line can prevent adequate amount of fuel from being supplied during Power Enrichment mode.

A restricted fuel filter can supply adequate amounts of fuel at idle, but may not be able to supply enough fuel during heavy acceleration.

Water or alcohol n fuel may cause low HO2S1 voltage during acceleration.

Check for adequate amount of fuel in the Tank.

When the engine is idling or at steady cruise, the HO2S1 voltage should vary from between approximately a00 to 900 millivolts. During power enrichment mode, more fuel is needed, and the HO2S1 should rise above 444 millivolts.

Check for faulty or plugged injector(s).

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

In order to detect engine misfire at higher engine speeds, the Engine Control Module (ECM) must know of any variation between the crankshaft sensor pulses. Most variations are due to the machining of the crankshaft reluctor wheel. However, other sources of variation are also possible. A Crankshaft Position (CKP) system variation learning procedure must be performed any time a change is made to the crankshaft sensor to crankshaft relationship of if the ECM is replaced or reprogrammed. The ECM measures the variations and then calculates compensation factors needed to enable the ECM to accurately detect engine misfire at all speeds and loads. A scan tool must be used to command the ECM to learn these variations. If for any reason the ECM is unable to learn these variations or they are out of an acceptable range, the ECM will set Diagnostic Trouble Code (DTC) P1336. An ECM that has not had the CKP system variation learning procedure performed due to replacement or reprogramming will also set DTC P1336.

DTC P1336 will only set if the ECM has not learned the CKP system variation. The ECM only needs to learn this variation once per life cycle of the vehicle unless the crank sensor to crankshaft relationship is disturbed. Removing a part is considered a disturbance. A fully warmed engine is critical to learning the variation correctly. If a valid learn occurs, no other learns can be completed that ignition cycle.

If the engine cuts out before the specified learn procedure engine speed or at normal fuel cutoff rpm, the ECM is not in the learn procedure mode.

The number(s) below refer to step(s) on the diagnostic table.

TThe Gravity Sensing Rough Road (G) sensor is a vertical low g-acceleration sensor. By sensing vertical acceleration caused by bumps or potholes in the road, the Engine Control Module (ECM) can determine if the changes in crankshaft speed are due to engine misfire or are driveline induced. If the G sensor detects a rough road condition, the ECM misfire detection diagnostic will be de-activated. The G sensor at rest output should be between 2.35-2.65 volts (+1G). During a rough road condition, the voltage output can vary between 0.5 (-1G) and 4.5 volts (+3G).

OR

Check for the following conditions:

Since the G sensor shares the ECM 5 volt reference and ground terminals with the A/C Pressure Sensor, a damaged A/C Pressure Sensor harness or sensor could cause a G sensor DTC to set. Refer to "Multiple ECM Information Sensor DTCs Set" in this section. in this section.

The G sensor will give correct voltages only if it is level and mounted securely to its bracket.

Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the con

The number(s) below refer to step(s) on the diagnostic table.

The Gravity Sensing Rough Road (G) sensor is a vertical low g-acceleration sensor. By sensing vertical acceleration caused by bumps or potholes in the road, the Engine Control Module (ECM) can determine if the changes in crankshaft speed are due to engine misfire or are driveline induced. If the G sensor detects a rough road condition, the ECM misfire detection diagnostic will be de-activated. The G sensor at rest output should be between 2.35-2.65 volts (+1G). During a rough road condition, the voltage output can vary between 0.5 (-1G) and 4.5 volts (+3G).

Check for the following conditions:

Since the G sensor shares the ECM 5 volt reference and ground terminals with the A/C Pressure Sensor, a damaged A/C Pressure Sensor harness or sensor could cause a G sensor DTC to set. Refer to "Multiple ECM Information Sensor DTCs Set" in this section.

The G sensor will give correct voltages only if it is level and mounted securely to its bracket.

Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

The number(s) below refer to step(s) on the diagnostic table.