1990 Geo Metro Base, 2D Hatchback, AutomaticFACTORY OEM SERVICE PROCEDURE

Engine Controls - Sensor Operating Range Charts: Introduction: Notes

Sensor operating range information can help determine if a sensor is out of calibration. An out-of-calibration sensor may not set a trouble code, but it may cause driveability problems.

NOTE: All voltage tests should be performed with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure.
AIR VALVE COOLANT TEMPERATURE SENSOR TEST

Temperature °F (°C) Valve Position
140 (60) Fully Closed
COOLANT TEMPERATURE SENSOR RESISTANCE

Temperature °F (°C) Resistance Ohms
-40 (-40) 100,700
0 (-18) 25,000
20 (-7) 13,500
40 (4) 7,500
68 (20) 3,400
100 (38) 1,800
160 (70) 450
212 (100) 185
MAP SENSOR VOLTAGE TEST

Altitude Feet (Meters) (1) Signal Voltage
Below 1,000 (304) 3.8-5.5
1,000-2,000 (304-610) 3.6-5.3
2,000-3,000 (610-914) 3.5-5.1
3,000-4,000 (914-1219) 3.3-5.0
4,000-5,000 (1219-1524) 3.2-5.8
5,000-6,000 (1524-1829) 3.0-4.6
6,000-7,000 (1829-2133) 2.9-4.5
7,000-8,000 (2133-2438) 2.8-4.3
8,000-9,000 (2438-2473) 2.6-4.2
9,000-10,000 (2473-3048) 2.5-4.0
(1) Measure voltage at appropriate ECU terminals. See WIRING DIAGRAMS .
MANIFOLD AIR TEMPERATURE (MAT) SENSOR RESISTANCE TEST

Temperature °F (°C) (1) Resistance Ohms
-40 (-40) 100,700
0 (-18) 25,000
20 (-7) 13,500
40 (4) 7,500
68 (20) 3,400
100 (38) 1,800
160 (70) 450
212 (100) 185
(1) Measure resistance across sensor terminals.
OXYGEN SENSOR VOLTAGE TEST

Condition (1) Volt
Lean .1
Rich .9
(1) Engine running in closed loop.
THROTTLE POSITION SENSOR (TPS) RESISTANCE TEST (METRO A/T ONLY)

Condition Resistance (Ohms)
Between Terminals A-B (1)(2) Continuity
Between Terminals A-B (1)(3) No Continuity
Between Terminals A-B (1)(4) Continuity
Between Terminals A-D (1)(4) 4,370-8,130
Between Terminals A-C (1)(4) 240-1,140
Between Terminals A-C (1)(5) 3,170-6,600
(1) See Fig 1 for terminal identification.
(2) With .012" (.30 mm) feeler gauge installed between stop screw and lever.
(3) With .035" (.89 mm) feeler gauge installed between stop screw and lever.
(4) Throttle valve at idle position.
(5) Throttle valve at wide open position.
Fig 1: Identifying Throttle Position Sensor Terminals (Metro A/T)
G121733Courtesy of GENERAL MOTORS CORP.
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