It's not a misfire, not the transmission -- what else could it be?

Here's a nice curveball that was thrown at a tech recently:  What could cause a vibration on acceleration if not a misfire or an issue with the transmission? Would you suspect the throttle position signal? The "Real Fix" below from Mitchell 1's SureTrack experience-based information resource is good example of how much a vehicle's behavior can change all because of an erratic throttle position signal.

Here's this vehicle's story – the customer complaint, the cause and the correction:

The Complaint

A customer with a 2005 Nissan Sentra (S, 1.8L) came into the shop saying that the check engine light was on and the vehicle vibrates upon acceleration.

The Cause

The tech performed a road test to duplicate the customer's concern and verified that the vehicle vibrated upon acceleration. When he connected a scan tool, he found code P2135. Entering the code into SureTrack, the Common Replaced Parts feature directed the tech to the throttle/pedal position sensor/switch "A"/"B" voltage correlation.

The tech then started the vehicle and allowed the engine to reach operating temperature. With the key on, engine off, he monitored live data on the scan tool, and observed the throttle position sensor A and throttle position sensor B voltages were erratic. The throttle position sensor A voltage should have been steady at 0.36 volts, and the throttle position sensor B voltage should have been steady at 4.36 volts. This gave him the information he needed to confirm his diagnosis and complete the repair: a faulty throttle position sensor.  

The Correction

Because the throttle position sensor is integrated into the throttle body and is replaced as an entire unit,  the tech replaced the throttle body, cleared codes, performed a road test and verified the vehicle operated properly. The check engine light did not illuminate and no fault codes returned.

Real Fixes from SureTrack are documented issues from actual shop repair orders and community discussions. You can read more Real Fixes in the Mitchell 1 Blog to see how SureTrack can help you correct issues that are not easily diagnosed using OEM information alone. SureTrack is currently available as a special free preview in the ProDemand repair information product.