Excerpt:"These are based on our Theory Car as described in the
Scan Tool Diagnosis Examples section. You
will notice the data is divided into frames as you would capture
and record data on your scan tool during a road test. Frame
'0' is where you pushed the button to record the data. And
since the scan tool was in the record mode, it remembered
data before you pushed the button that so you could review
it later and see what was going on with the vehicle when it
messed up. These are the '-1', '-2', '-3' etc... frames. Good
luck!
1. Use the following scan tool data for this question. The
engine is idling in the shop. It has a regular engine miss
and has failed a smog inspection at idle with high CO. What
is the likely problem with this Theory Car engine?
| Frame |
-8
|
-7
|
-6
|
-5
|
-4
|
-3
|
-2
|
-1
|
0
|
| TPS: (v) |
1.0 |
1.0 |
1.0 |
1.0 |
1.0 |
1.0 |
1.0 |
1.0 |
1.0 |
| MAP: (v) |
1.3 |
1.3 |
1.3 |
1.3 |
1.3 |
1.3 |
1.3 |
1.3 |
1.3 |
| ECT: (v) |
0.5 |
0.5 |
0.5 |
0.5 |
0.5 |
0.5 |
0.5 |
0.5 |
0.5 |
| O2: (v) |
0.3 |
0.0 |
0.2
|
0.1
|
0.0
|
0.0
|
0.1
|
0.3
|
0.0
|
| RPM: |
800 |
800 |
810 |
800 |
810 |
800 |
810 |
800 |
800 |
| INJ: (ms) |
2.9 |
2.9 |
2.9 |
2.9 |
3.0 |
3.0 |
3.0 |
3.1 |
3.1 |
| LFTRIM: (%) |
+15 |
+15 |
+15 |
+15 |
+16 |
+16 |
+16 |
+17 |
+17 |
A: MAP sensor vacuum line fell off
B: Fuel pressure too high
C: ECT voltage too high
D: Fouled #2 spark plug
2. This Theory Car engine runs very rich and gets very poor
fuel economy. Using the scan tool information below, what
is the likely problem?
| Frame |
-8
|
-7
|
-6
|
-5
|
-4
|
-3
|
-2
|
-1
|
0
|
| TPS: (v) |
1.0 |
1.0 |
1.0 |
1.0 |
1.0 |
1.0 |
1.0 |
1.0 |
1.0 |
| MAP: (v) |
1.1 |
1.1 |
1.1 |
1.1 |
1.1 |
1.1 |
1.1 |
1.1 |
1.1 |
| ECT: (v) |
4.7 |
4.6 |
4.7 |
4.7 |
4.8 |
4.7 |
4.7 |
4.7 |
4.8 |
| O2: (v) |
0.9 |
0.9 |
0.9
|
1.0
|
1.0
|
0.9
|
0.9
|
0.9
|
0.9
|
| RPM: |
800 |
800 |
810 |
800 |
810 |
800 |
810 |
800 |
800 |
| INJ: (ms) |
2.9 |
2.8 |
2.9 |
2.9 |
3.0 |
2.9 |
3.0 |
2.9 |
2.9 |
| LFTRIM: (%) |
-4 |
-4 |
-4 |
-4 |
-4 |
-4 |
-4 |
-4 |
-4 |
A: Poor electrical connection at ECT sensor
B: Bad thermostat
C: Low battery voltage
D: Plugged catalytic converter"
The article contains these sections:
- 15 Questions
- Answers and Explanations
