COOLANT TEMPERATURE GAUGE ON RED MARK. Saturn Saturn 1991

For 1990-2009 cars

# COOLANT TEMPERATURE GAUGE ON RED MARK

#### SUBJECT: Coolant Temperature Gage Needle at, or on the RED Mark (Diagnose Coolant Temperature Sensor Circuits)

Due to the addition of "MODELS AFFECTED" with a VIN breakpoint, this bulletin supersedes bulletin 91 - T - 18, which should be discarded.

#### MODELS AFFECTED: 1991 Saturns built before vehicle identification number (VIN) MZ105000.

CONDITION: Customers express concern that vehicle is overheating since temperature gage needle is at, or on the RED mark of the temperature gage.

CORRECTION: Diagnose engine coolant temperature indicator sensor, coolant temperature gage, powertrain control module and/or coolant temperature indicator - PCM sensor (CTS) according to the following procedures.

#### NOTE: The normal operating range of the engine coolant temperature gage is shown in Figure 1. When the gage reads just above 3/4 mark, the coolant should be approximately 105.5 degrees Celsius (222 degrees Fahrenheit) and the engine cooling fan should turn on and cool the cooling system. The engine cooling fan will turn off at approximately 100.5 degrees Celsius (213 degrees Fahrenheit), and the temperature gage should read around the 1/2 mark.

#### PROCEDURE:

-------- Description: ----------- The engine cooling fan and hot telltale lamp are controlled by the powertrain control module (PCM). The PCM monitors the coolant temperature indicator - PCM sensor (CTS) that is located on the lower left, rear side of the cylinder head (Figure 2) and will turn on the engine cooling fan when the coolant temperature reaches approximately 105.5 degrees Celsius (222 degrees Fahrenheit). This sensor is connected to the PCM by two wires. The coolant temperature gage is controlled by the single wire engine coolant temperature indicator sensor that is located on the upper left, rear side of the cylinder head (Figure 2).

During certain conditions (hot days, under heavy vehicle loads, air conditioning on, pulling a trailer, extended idling, etc.), the coolant temperature gage may read higher than the normal range indicated in Figure 1. This is normal for high-ambient and load conditions. If the coolant temperature gage reads at, or on the RED zone, or if the hot telltale lamp comes on, there is a concern and the following procedures must be performed to diagnose and correct this condition.

1. Verify that no diagnostic codes are present in the current or malfunction history of the PCM.

2. Inspect the engine cooling system. Refer to "Cooling System" section of the "Engine Mechanical Service Manual."

3. Verify proper engine cooling fan operation. Monitor the engine cooling fan with the portable diagnostic tool (PDT). The engine cooling fan should turn on when the coolant temperature reaches approximately 105.5 degrees Celsius (222 degrees Fahrenheit). If engine cooling fan does not turn on, refer to the "Cooling System" section of the "Engine Mechanical Service Manual."

4. Remove front air intake duct assembly for access to both the coolant temperature indicator - PCM sensor (CTS) and the engine coolant temperature indicator sensor. (For DOHC [LLO] engines, refer to "Air Cleaner Housing and Cross-Car Duct Assembly" procedures in the "DOHC [LLO] Engine Fuel/Intake" Section of the "Fuel/Air Intake/Exhaust Service Manual.")

#### IMPORTANT: If the engine induction air temperature sensor (ATS) is unplugged, a PCM code 23 will set. Clear PCM code 23 after installing air cleaner at the end of these procedures.

5. Disconnect the single wire electrical connector from the engine coolant temperature indicator sensor. Using grey pigtail jumper P/N 12117087, plug jumper into the sensor.

IMPORTANT. Do not disconnect the coolant temperature indicator - PCM sensor (CTS) at this time.

6. Run the engine until the PDT indicates that the coolant temperature is above 85 degrees Celsius (185 degrees Fahrenheit).

#### IMPORTANT: Engine coolant temperature must be above 85 degrees Celsius (185 degrees Fahrenheit) for the test to be accurate.

7. Turn the ignition OFF and immediately disconnect the coolant temperature indicator - PCM sensor (CTS) (two - wire connector) and install the black pigtail jumper P/N 12117086. Use the Saturn digital volt ohmmeter (DVOM), set to the "2K OHM" scale. Take the resistance reading across the jumper leads of the sensor and record the reading. Next, take the resistance reading from the single wire jumper to ground on the engine coolant temperature indicator sensor and record.

#### IMPORTANT: The proper gage pin leads may be used for resistance checks instead of pigtail jumpers.

Subtract the lower resistance reading from the higher resistance reading, the difference should be 85 ohms or less. If the sensors have a resistance reading greater than 85 ohms of each other, proceed to Step 9. If both sensors are within 85 ohms of each other, proceed to Step 10.

#### CAUTION:

STEAM AND SCALDING LIQUIDS FROM A HOT COOLING SYSTEM CAN BLOW OUT AND BURN YOU BADLY. THEY ARE UNDER PRESSURE, AND IF YOU TURN THE COOLANT SURGE TANK PRESSURE CAP, EVEN A LITTLE, THEY CAN COME OUT AT HIGH-SPEED. NEVER TURN THE PRESSURE CAP WHEN THE ENGINE AND COOLING SYSTEM ARE HOT. WAIT FOR THE ENGINE TO COOL BEFORE REMOVING THE PRESSURE CAP

8. For sensor readings greater than 85 ohms of each other, proceed with the following steps:

#### NOTE: Refer to "Coolant Temperature Sensor" in the "Powertrain Control Module" Section of the "Electronic Engine Controls Service Manual", for the coolant temperature indicator - PCM sensor (CTS) removal and installation procedures.

a. Remove the coolant temperature indicator - PCM sensor (CTS) and allow it to cool to room temperature.

b. Using the Saturn DVOM on the "20K OHM" scale, measure resistance and compare to the following chart. If the coolant temperature indicator - PCM sensor (CTS) is within specifications, replace engine coolant temperature indicator sensor and re - install the coolant temperature indicator - PCM sensor (CTS) back into the engine. If the coolant temperature indicator - PCM sensor (CTS) is not within specifications, replace with a new sensor and re-install engine temperature indicator sensor back into the engine.

Coolant Temperature Indicator - PCM Sensor (CTS) (Resistance between terminals) Temp (Deg. Celsius) Temp (Deg. Fahrenheit) -------------------------------------------------------------------------- 3.3Q to 3.7kQ 20 68

3.1Q to 3.6kQ 21 70

3.0Q to 3.4kQ 22 72

2.9Q to 3.3kQ 23 73

2.7Q to 3.1kQ 24 75

2.6Q to 3.0kQ 25 77

2.5Q to 2.9kQ 26 79

2.4Q to 2.7kQ 27 80

Sensor Part Number ------ ----------- Engine Coolant Temperature 21020124 Indicator Sensor Coolant Temperature Indicator 21020104 PCM Sensor (CTS)

c. Test engine cooling system operation following the procedures in Steps 11 and 12.

9. For sensors that are within 85 Ohms of each other, proceed with the following steps:

a. Disconnect negative battery terminal.

b. Remove upper trim panel screw caps by carefully prying with a small flat-head screwdriver.

c. Remove upper trim panel screws.

d. Lift upper trim panel to disengage clips at rear edge.

e. Pull panel rearward out of the clips at the bottom of the windshield.

f. Remove upper trim panel.

#### NOTICE: Start at the bottom clips and work up to the top clips. Do not use any instrument that may damage the trim panel.

g. Carefully remove center air outlet/trim panel by pulling outward at clip location.

h. Open the glove box.

i. Remove screws and pull cluster trim panel rearward to disengage retainers.

j. Remove connector position assurance (CPA) devices and disconnect the electrical connectors from the instrument panel lighting and rear window defogger switches.

k. Remove the cluster trim panel.

l. Remove screws and pull instrument cluster assembly out enough to disconnect electrical connectors.

m. Replace the instrument cluster. Check the part number on the colored label against the following chart. If the instrument cluster is a "Current Instrument Cluster Asm," replace with a "Replacement Instrument Cluster Asm." The Replacement Instrument Cluster Asm is ordered through the Parts department and is received with the vehicle's mileage already set by the factory. The replacement instrument cluster must be received before replacing the current instrument cluster.

Current Replacement Instrument Instrument Cluster Asm Cluster Asm ----------- ----------- 21021073 21021209 21021074 21021210 21021075 21021211

n. Disconnect electrical connectors, by depressing the retainer tabs, and remove the instrument cluster assembly.

o. Connect electrical connectors on instrument cluster assembly.

#### IMPORTANT: Make sure electrical connectors for instrument panel lighting and rear window defogger switches are in place.

p. Install instrument cluster assembly and screws.

#### IMPORTANT: When replacing instrument cluster assembly, use new wax dip screws P/N 21040914.

q. Position cluster trim panel to instrument panel.

r. Connect electrical connectors on instrument panel lighting and rear window defogger switches and install CPA devices to electrical connectors.

s. Install cluster trim panel into retainers.

t. Install and tighten screws.

u. Install center air outlet/trim panel, by pushing in at clip locations.

v. Install upper trim panel by inserting it into clips at windshield and snapping rear of panel into place.

w. Install upper trim panel screws and screw caps.

x. Connect negative battery terminal.

y. Set clock to proper time.

10. Remove jumper pigtails and connect the electrical connectors to both sensors. Install air cleaner duct assembly and verify that the electrical connector to the engine induction air temperature sensor is connected. Clear PCM codes set during testing procedures.

11. Start the engine and monitor the coolant temperature gage. Run the engine until the engine cooling fan turns on. Verify that the temperature gage readings compare with Figure 1, and that the customer concern is eliminated.

PARTS REQUIREMENTS: Model Codes Usage ------- ----- 21020124 Engine Coolant __ LLO & LKO Temperature Indicator Sensor Assembly Replacement

21020104 Coolant Temperature __ LLO & LKO Indicator-PCM Sensor Assembly

21021209 Cluster Asm - Inst B69 LKO & MP2 & J41

21021210 Cluster Asm - Inst B69 LKO & JL9 & MP6

21021211 Cluster Asm - Inst B27, D69 LKO & JL9 & MP6

CLAIM INFORMATION: To receive credit for this repair, submit a warranty claim through the Saturn Dealer System using one of the labor operations listed below:

Labor Case Operation Type Description Code Time --------------------------------------------------- VW Engine Coolant N2230 0.7 hrs Temperature Indicator Sensor Assembly Replacement

VW Coolant Temperature J6368 0.7 hrs Indicator-PCM Sensor

Assembly Replacement VW Instrument Cluster N4180 0.6 hrs Assembly Replacement

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.