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| Diagnostics: |
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| A. |
Checking for Computer
Codes OBD-I / IEEC-IV (1989 - 1995) |
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| B. |
Checking for Computer
Codes OBD-II / IEEC-V (1996 - 1998) |
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| C. |
E4OD sensors: (1989
- 1998) |
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| A. |
Checking Computer Codes OBD-I / IEEC-IV (1989 - 1995) |
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| Perform the Key On Engine Off (KOEO) self test. |
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| 1. |
Connect jumper and (optional test light or volt meter) as described in Figures OBD-1
A & B below. |
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NOTE: Turn off A/C during this
test. |
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| 2. |
Turn Key off, then on, then off, then on, then off, back on |
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ON - OFF - ON - OFF - ON - OFF - ON
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| 3. |
Display pulse codes will now show on instrument panel "Check Engine Light"
and optional test light / volt meter. |
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| Deleting Codes from Computer Memory: |
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| 1. |
Start KOEO test as described above. |
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| 2. |
Remove Jumper from from test connector once light begins to flash. |
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Codes should now be erased from Keep Alive Memory in computer. |
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| Resetting Computer and Clearing Keep Alive Memory: |
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| 1. |
Disconnect battery for minimum of five (5) minutes. |
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Keep Alive Memory should now be cleared. |
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| 2. |
Vehicle must be driven for at least 10 miles of normal shifting driving on local
and highway for OD so computer will relearn proper control based on sensor data. |
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| 3. |
Conduct all recommended sensor and electronic transmission tests. |
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| Using "Check Engine Light" to read computer pulse codes - |
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Install jumper wire From test connector to Pin 2 on of computer connector as shown
in figure OD1-A below. |
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FIGURE OBD-1 A
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| Using Test Light or Analog Ohm Meter
(with sweep needle - Not a digital meter) |
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Install jumper wire from test connector to Pin 2 on hook up connector; and
Install test light or volt meter +
lead to battery +
terminal and - lead to Computer
Connector as
shown in figure OD-I B below. |
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FIGURE OBD-I B
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Back to Top |
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| B. |
Checking for Computer Codes OBD-II / IEEC-V (1996 - 1998) |
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This requires using a Scantool Reader to read and display codes from the IEEC-V computer |
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At least one major Automotive Parts Chain loans a scantool to customers (Deposit
required) |
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| NOTE: |
Most Scantool Readers for OBD-II are fairly easy to use but, each
tool is different. |
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You will need to become familiar with the particular Scantool Reader
instructions to properly scan, display and delete codes from the computer's memory. |
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Back
to Top |
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| C. |
E4OD sensors: |
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| MLPS - Manual Lever Position Sensor - |
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| MLPS is located on transmission manual shift lever - (drivers
side) |
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| Symptoms: |
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Vehicle won't start in Park and/or Neutral or will start in one
or but not the other
Computer codes 67, 634, 654, (A/C must be off when testing system)
Vehicle appears to be in wrong gear: i.e., Forward in Neutral
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| TPS - Throttle Position Sensor (Gas Engines)
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| FIPL - Fuel Injection Pump Lever Sensor
(Diesel Engines same as TPS above) |
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| TPS is located directly on the Throttle body lever. |
| FIPL is located on the high pressure fuel pump lever. |
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| Symptoms: |
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Harsh / low or high shift efforts - consistent.
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Check for computer codes 23, 53, 73, 167
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| VSS - Vehicle Speed Sensor - |
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| VSS is located either on speedometer gear cable at tailshaft of transmission; or |
| VSS is located on top of rear differential. |
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| Symptoms: |
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Very Erratic Shift Points
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Computer codes 23, 53, 73,
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Checking for bad sensor or connector: |
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| 1. |
Check each connector condition and for good contact.
Connectors under vehicle can be contaminated with water, mud, etc.
Clean connector contacts with contact cleaner and emery board (fiber finger nail file) as needed. |
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| 2. |
Visually inspect each wire for breaks from sensor back to firewall bulkhead connector. |
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Run continuity test on wires from sensor to bulkhead connector at firewall.
Refer to proper vehicle wiring diagram to located appropriate pins on connectors and color of wire to trace.
NOTE:
Disconnect sensor connector and negative cable on battery prior
to using a ohm meter as they have current which could damage the vehicle computer.
Insert sharp probe in to wire near bulkhead connector and check for continuity at sensor connector. You may have
to use a long piece of wire to do the continuity test.
Repeat test for each wire. |
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| 3. |
Adjust TPS or FIPL sensor per manual instructions for your particular vehicle
You will be looking for 5 volts and a lower return voltage back to computer with engine off, at idle and then at
full open throttle.
NOTE for FIPL (Diesel Engines):
If you have a Black colored FIPL sensor, replace this sensor with a Gray colored update.
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| 4. |
Adjust the MLPS by aligning notices in shifter shaft with alignment notch in side
(toward top) of sensor.
Also, shift to Neutral and verify mark on MLPS is aligned properly. (not all after market makers of the MLPS use
this neutral position mark). |
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