Table of Contents
Advertisement
High idle speed
Low idle speed
Surging idle
18.0 TESTING AND TROUBLESHOOTING ELECTRICAL COMPONENTS
18.1 Testing Relays
1 - To test the relays, apply a 12 volt power source to terminal 85 and ground terminal 86. The relay should click. Using an
ohm meter, check for low resistance across terminals 87 and 30.
2 - With the 12 volt power source removed from terminal 85, check for high resistance across terminals 87 and 30.
3 - If the relay does not perform as described above, the relay is defective and must be replaced.
18.2 Testing The Manifold Absolute Pressure (MAP) Sensor
One way to check the MAP sensor is to monitor the system with the software. Check the map sensor readings with the engine
turned off. It should be fairly close to 101 kPa at sea level and decrease by about 3.4-3.5 kPa per 1000 feet elevation above sea
level. The MAP value may also vary a small amount due to weather conditions. The table below shows MAP values in kPa
compared to the more familiar units of in Hg. The second column is gauge pressure in Hg and the third column is vacuum in
units of in Hg.
MAP Value (as read on the computer)
101 kPa
90 kPa
80 kPa
70 kPa
60 kPa
50 kPa
40 kPa
30 kPa
20 kPa
NOTE:
Users at higher altitudes will have MAP values lower than 101 kPa as described in the above paragraph along with a
lower corresponding manifold pressure. However, the vacuum on a typical vacuum gauge is referenced to ambient
conditions and will read 0.0 with no engine vacuum regardless of MAP value unlike the sea level based third column
in the above table. A MAP value lower than 20 kPa is most likely an indication of a bad MAP sensor connection or a
MAP sensor problem.
1 - If you do not have a PC, use a digital voltmeter and tap into the ORANGE wire at the MAP sensor. With the engine off
and the key in the run position, voltage should be close to 2.0 volts.
2 - Connect a hand vacuum pump to the MAP sensor with the key in the run position. Using the vacuum pump, the MAP
sensor can be checked at the following vacuums. Voltage output should be close to these values.
20" Hg vacuum
15" Hg vacuum
10" Hg vacuum
5" Hg vacuum
- MAP sensor hooked up improperly
- Faulty MAP sensor
- Faulty coolant temperature sensor
- Idle speed not adjusted correctly
- Binding or sticking throttle linkage
- Faulty IAC motor
- Faulty ECU
- TPS adjusted incorrectly
- Idle speed not adjusted correctly
- Faulty IAC motor
- Faulty ECU
- TPS adjusted incorrectly
Engine running rich
Engine running lean
Idle trim not adjusted correctly
MAP Value to Manifold Pressure Value to Vacuum Comparison
Manifold Pressure Value (in Hg)
- Using vacuum gauge, ensure MAP sensor is hooked
up to full manifold vacuum
- See Testing MAP Sensor section
- See Testing Coolant Temperature Sensor section
- Set idle speed. See Item 4 in Tuning and
Adjustments section
- Find cause of binding or sticking and correct.
- See Testing IAC section
- Replace ECU
- See Tuning and Adjustments section
- Set idle speed. See Item 4 in Tuning and
Adjustments section.
- See Testing IAC section
- Replace ECU
- See Tuning and Adjustments section
- See Item 3 above
- See Item 4 above.
- See Tuning section
Vacuum (in Hg) Relative to Ambient
Pressure Condition (sea level)
29.7
26.5
23.5
20.6
17.6
14.7
11.8
8.8
5.9
.55 volt
1.0 volt
1.4 volts
1.9 volts
0.0
3.2
6.2
9.1
12.1
15.0
17.9
20.9
23.8
29
Advertisement
Table of Contents
Troubleshooting
