Following a sound diagnostic practice leads to sound vehicle repairs. The subject vehicle for this article is a 2007 Toyota Tundra SR5 with a 5.7 I-force engine (350 C.I.D.), automatic transmission, and 48,564 miles (78,156 KM) on the vehicle odometer. The customer complaint is hesitation during cold driving, and a very active throttle feeling during warm driving. The second complaint was poor fuel economy since the problem started.
Let’s begin with the first step verify the complaint. The technician decided to install the scan tool for the test drive. Key-On-Engine-Off scan for codes revealed no diagnostic codes (DTC) in any of the vehicle computers. The Key-On-Engine Run test was done while viewing engine computer data and the scan tool was set to capture data during the test drive to verify the complaint. The first thing the technician noticed was the Battery; engine RPM and timing readings on the scan tool were very erratic. During the test drive the vehicle did hesitate. As the vehicle warmed-up the hesitation was less noticeable. Once back in the shop the captured test files were reviewed by the technician. The technician noticed that the readings were erratic on the scan tool until the vehicle had been driven for a while. The technician noticed that the reading somewhat stabilized after the vehicle had warmed-up.
The technician then proceeded to perform a visual inspection and noticed that the battery cables were in need of service along with the battery it was dirty and appeared to be wet. No other problems were found on the visual inspection. The service technician requested a battery service and battery test, charging system, and cranking system analysis.
The technician then preceded to look-up any Technical Service Bulletins (TSBs) that matched the customer complaint. There were no technical service bulletins that matched the customer complaint. The technician then analyzed the data he collected during the diagnostic process and determined that the only verifiable repair in his diagnosis was the battery and cable faults. This would be a valid suspect to resolving the customer complaint. The battery and battery cables are the heart of all the electrical systems in the vehicle.
The technician isolated the problem to the battery issue and began his pin point test. The open circuit voltage on the battery was 12.4 volts. Connecting the volt meter negative (-) lead to the negative battery post and using the positive meter lead to check for voltage present on the top of the battery. The meter was set to read DC volts. This test revealed a reading of 7.48 volts as a high and 4.25 volts as a low leaking out of the top of the battery. The battery was charged and cleaned up. The cables were serviced. The battery load test was failed by the battery. The battery was replaced.
The technician reexamined the customer complaint and based on what he had found and repaired concluded that he may need more analysis or the vehicle was repaired.
The next morning the technician installed the scan tool and performed a Key-On-Engine-Off scan for codes, none were found. He set the scan tool to capture files during the verify repair test drive. The technician started the vehicle and observed that the battery, engine RPM and timing readings were no longer erratic. He drove the vehicle for several miles and did not have any hesitation at all.
Conclusion; following a diagnostic process uncovered a simple problem causing what appeared to be a high tech problem. The battery service and battery replacement solved the complaint. The customer reported several weeks later that fuel economy was back to normal and even doing a little bit better!