| Subject: | Information on Normal APP and TP Signal Circuit 2 Voltage Fluctuation |
| Models: | 2004-2006 Buick Rainier |
| 2005-2006 Chevrolet Cobalt |
| 2004-2006 Chevrolet Colorado |
| 2002-2006 Chevrolet TrailBlazer |
| 2002-2004 Oldsmobile Bravada |
| 2005-2006 Pontiac Pursuit (Canada Only) |
| 2004-2006 Chevrolet Malibu |
| with 2.2L Engine (VIN F - RPO L61) |
| with 2.2L Engine (VIN D - RPO L61) |
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
If the APP sensor 2 or TP sensor 2 signal circuit is monitored with an oscilloscope or Fluke 87 DVOM on the 1 ms min/max setting, it may be noted that the signal voltage decreases every 156 ms for 6.25 - 7.8 ms each time.
Recommendation/Instructions:
It is normal for these voltages to drop as described above. This is the result of the PCM testing the APP and TP sensors for internal shorts. During the PCM test for a DTC P2135 (P1221 on 02-03 Vue), the PCM shorts the TP sensor 2 signal to ground every
156 ms for 6.25 - 7.8 ms each time. During the PCM test for a DTC P2138 (P1271 on 02-03 Vue), the PCM shorts the APP sensor 2 signal to ground every 156 ms for 6.25 - 7.8 ms each time. At this time, the PCM monitors the APP sensor 1 and TP sensor 1 signal
circuit voltages to ensure that they do not decrease with the sensor 2 signal circuits. If they do, an internal sensor short is present or the signal circuits are shorted together.
If there are no DTCs resetting but toggling voltages are encountered during inspection with an oscilloscope or Fluke 87 DVOM on the 1 ms min/max setting, no repairs should be attempted to prevent the voltages from toggling as it is a normal condition.
If DTCs are resetting, follow the related SI diagnostic charts to diagnose the ETC system.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
