Stranger Things
Have Happened
by Mike Souza
www.atra.com
Figure 1 Figure 2
T
he first two strange occurrenc- tial cause of the problem, try driving try before replacing the alternator on
es involve Chevy trucks with a the vehicle with the alternator discon- Dodge vehicles.
6.5L diesel engine and 4L80E nected. Now back to the Chevy shift shut-
transmission. EMI is an all-too-common problem tle: In this case the symptom was
Problem 1: The vehicle displays on many vehicles, foreign or domestic. caused by the pump cam optical sensor/
intermittent hard starting, with no codes The ATRA HotLine logs calls almost fuel temperature sensor, mounted on
stored, and a transmission shift shuttle daily on speed sensor problems caused top of the injection pump (figure 2).
on the 2-3, 3-2 and 3-4, 4-3 shifts at by EMI due to faulty sensor grounds. According to GM, the injection
25% throttle or higher. The most common complaint is pump cam sensor is an optical sensor.
Scan data reveals the shift shuttle TCC shuttle on Dodge rear wheel drive It receives a 5-volt reference signal that
is being commanded by the PCM. This vehicles, caused by EMI interfering allows the PCM to measure fuel injec-
particular vehicle was equipped with with the TPS signal. On those vehi- tor pulse ring RPM and position. The
drive by wire; (no TPS). The accelera- cles poor grounds will cause the same PCM uses this signal to control fuel
tor pedal position sensor (APPS) signal symptom, so clean and tighten the bat- injection timing. The PCM compares
seemed to be working fine (figure 1). tery terminals no matter how good they this signal with the crankshaft position
A failing alternator causing too look. Then unbolt and clean the battery (CKP) sensor (figure 3) for diagnostic
much electromagnetic interference ground cable on the engine block as purposes. The fuel temperature sensor
(EMI) can cause this shift shuttle. To well (both batteries and grounds on works like an intake air temperature
eliminate the alternator as a poten- diesel engines). Always give this a (IAT) sensor to control fuel volume.
26 GEARS January/February 2010
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74