Shift Pointers
- Author: Wayne Colonna, Technical Editor
- Subject Matter: 2014 Nissan Versa
- Issue: Power loss
A 2014 Nissan Versa arrives at a shop on a flatbed with a customer complaint of a loss of engine power. The reason it was brought to a transmission shop is the type of engine power loss it had. In park or neutral, the engine can rev up to 2500 rpm easily. Even in drive with the brakes applied, you can reach stall speed torque with no power loss issues at all. But, the moment the brake is released to launch forward, as soon as it starts to roll there is an immediate loss of engine power. The scan tool immediately shows the throttle opening only going to 3% with no throttle response, meaning the throttle body is in default. Yet when brake torqueing in drive you can see as much as 81% throttle opening.
The technician diagnosing the vehicle had the TCM disconnected checking power and grounds and other inputs. The vehicle needed to be moved. Another person jumped in, started the vehicle, put it in drive and it drove forward with no power loss. Surprised by this, they drove it a bit further when it suddenly returned to a no-throttle-response condition.
Out of curiosity, the TCM was reconnected while the ABS module was disconnected. The vehicle performed normally in that it did not experience a loss of power. It always had a normal throttle response. This made the ABS module appear to be the offending culprit. Looking at the brake lights, all were working, nothing looked unusual there. This prompted the replacement of the ABS Module. After installing the new module, it only produced a heartbreak. The same throttle body default occurred upon the release of the brake.
After speaking to the owner of the vehicle, it was discovered that the problem began after having new brake bulbs put in. According to the dealer, 17916 are the correct bulbs for this application. When the bulbs were removed that began the problem, it was discovered that 1157 bulbs were used.
At first glance, the 1157 bulb and the 17916 bulb looked alike. But a closer inspection revealed that the 1157 bulb uses a coil filament while the 17916 bulb uses a solid wire filament. The coil filament drew more current than the solid wire filament. In other words, when the brakes are not applied, there is a small amount of current in the brake light circuit that the computer uses to monitor the integrity of the circuit. The added amount of current draw caused by the incorrect brake bulbs was enough to trigger the throttle body default mode. A DTC would have sure been helpful but there was none. From all the codes looked at, it doesn’t appear to have one or more assigned to such a discrepancy. A P1805 is a brake switch circuit open or shorted. A C1116 is also a stop lamp switch code. It would have been nice if one of these had set. But the parameters here are looking at brake switch activity, which operates at much different amperage levels.
“How could the wrong bulb be installed in the first place?” may be something you are asking yourself if you are inquisitive. When buying brake bulbs at an auto part store, they many times have cross reverence charts to match up with aftermarket products. In this case, the cross reference was wrong:
Wagner 17916 (Dual Circuit) = 1016 1034 1076 1077 1130 1154 1157 1158 1493 2057 2357 2397 7528 2F2112011
Watch your brake bulbs, they can cause heartbreak.
