Question about 1999 Pontiac Grand Am GT

1 Answer

Need a wiring diagram of the 2 wires from the temp sending unit that controls the temp gauge and cooling fans on a 99 grand am gt. Need to see where they go They disappear behind the engine

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  • Jeff Armer Nov 13, 2016

    Powertrain Control Module
    Below the left side of the IP near the steering column

  • Jeff Armer Nov 13, 2016

    That is where the wires are going to.

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  • Pontiac Master
  • 15,575 Answers

The PCM regulates voltage to the coolant fan relays, which operate the fans. Refer to Engine Controls.

Engine Cooling Fan Description - Electric
The electric cooling fans are used to lower the temperature of the engine coolant flowing through the radiator. They are also used to cool the refrigerant (R-134a) flowing through the A/C condenser.
Operation
The electric cooling fan operates when the engine cooling temperature exceeds a certain value. The cooling fan on this engine is controlled by the PCM. The cooling fan has one speed. The PCM turns the cooling fan ON by grounding the coil of the cooling fan relay when certain conditions are met. When the A/C is requested, the cooling fan will also be turned ON.
Power for the cooling fan motors are supplied through Cool Fan #1 and Cool Fan #2 relays. The cooling fan relays are energized when current flows from the fuses in the Cell 23: Cooling Fan Controls , and through the relay coils to ground through the PCM. The Low Speed fans control circuit is grounded for low speed fans operation. During low speed fans operation, both fans run at a slow speed. The High Speed fans control circuit is grounded for high speed operation. During high speed fans operation, both fans run at high speed.
Important: When certain Diagnostic Trouble Codes (DTCs) are present, the PCM may command the cooling fans to run all the time. It is important to perform Powertrain On Board Diagnostic (OBD) System Check prior to diagnosing the engine cooling fans.
If a problem that involves the low speed cooling fan relay control circuit exists, DTC P0480 should set. If the problem affects the high speed cooling fan relay control circuit, DTC P0481 should set. A problem with the ECT sensor should set DTC P0117, P0118, P1114, or P1115. Any of these DTCs will affect cooling fan operation and should be diagnosed before using the Cooling Fan Diagnosis tables. The Cooling Fan Diagnosis tables should be used to diagnose the PCM controlled cooling fans only, if a DTC has not set.

The engine coolant temperature (ECT) sensor (3) is a thermistor, a resistor which changes value based on temperature, mounted in the engine coolant stream. Low coolant temperature produces a high resistance (100,000 ohms at -40°C) (-40°F), while high temperature causes low resistance (70 ohms at 130°C) (266°F).
The PCM supplies a 5 volt signal to the ECT sensor through a resistor in the PCM and monitors the terminal voltage. Since this forms a series circuit to ground through the ECT sensor, high sensor resistance (low temperature) will result in high PCM terminal voltage. When the resistance of the ECT sensor is low (high temperature), the terminal voltage will be drawn lower. This terminal voltage indicates engine coolant temperature to the PCM.
A hard fault in the ECT sensor circuit should set either a DTC P0117 or P0118. Remember, these DTCs indicate a malfunction in the engine coolant temperature circuit, so proper use of the DTC table may lead to either repairing a wiring problem or replacing the sensor, to properly repair a problem.

The engine coolant sensor is an input to the PCM , Two wire's both go to the PCM .An the PCM turns on the cooling fans !

DTC P0480 Cooling Fan Relay 1 Control Circuit
DTC P0481Cooling Fan Relay 2 Control Circuit
The Body Control Module (BCM) request the cooling fans. The BCM sends a Class 2 message to the PCM in order to enable the fans based on various inputs. Thebattery voltage travels to all three cooling fan relay coils. The PCM enables cooling fan relay #1 by providing the ground path. The PCM enables cooling fan relays #2 and mode control together by providing a ground path. The left and right cooling fans are connected in series. This will enable both fans on low speed when the fan #1 relay is energized. When all three fan relays are energized, both fans will operate at high speed. The high speed is possible because the fan relays are wired in a parallel circuit. When the PCM detects that certain DTCs are set, the PCM will enable the cooling fans.
The PCM will enable the engine cooling fans when certain Diagnostic Trouble Codes are set.

Important: A short to ground will cause an open fuse(s). Before performing this diagnostic procedure, inspect the fuse(s) for an open.
1
Did you perform the Instrument Cluster System Check?
--
Go to Step 2
Go to Instrument Cluster System Check
2
Turn the ignition switch to the ON position.
With the scan tool select Instrument Panel Cluster, Special Functions, Instrument Panel Cluster (IPC) gauges.
Perform the Coolant Gauge Sweep Test.
Does the coolant temperature gauge complete a full sweep when commanded?
--
Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls
Go to Step 3
3
Replace the instrument cluster. Refer to Instrument Cluster Replacement .
Did you complete the repair?
--
Go to Instrument Cluster System Check
--

Your best bet would be to take your vehicle to a qualified repair shop that knows how the system works . An has the tools to diagnose the problem .

Posted on Nov 13, 2016

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Posted on Jan 02, 2017

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SOURCE: need wireing diagram for 2002 dodge grand caravan

------>>>FRONT>>>>of Van >>>>

______________________________
#5 cyl #6 cyl

#3 cyl #4 cyl

#1 cyl #2 cyl
______________________________
_________________
I COIL BLOCK I
I I
I #3 #1 #5 I
I I
I I Firing Order Is
I I 1 2 3 4 5 6
I #6 #4 #2 I
I _______________I_

the Wires Go Accordingly to prospective Terminals, So Sorry Unable to Send Pics through FixYa, A Formating Problem Exists
and they show on my end but not on your end this is TRUE and CORRECT To The BOOK other than the Lines from Coil to Spark Plug ENDS at CYLINDERS. Please dont Forget to RATE Me
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Posted on Mar 27, 2009

  • 101 Answers

SOURCE: 2002 Jeep Grand Cherokee 4.0L oil pressure gauge reading too high

if the gauge starts a 0 - goes to 1/2 , than full - sounds like gauge is OK - seems to me like the sending unit is bad - you could try removing the sender and trying to clean out the port with "brake clean", letting it dry than re-installing it. the pressure switch is still the least expensive place to start

Posted on Oct 27, 2009

  • 1 Answer

SOURCE: 1987 camaro iroc-z . need wiring diagram for

electric fans not going on causing engine to overheat

Posted on Oct 09, 2010

cool78259
  • 228 Answers

SOURCE: temp gauge doesnt work on my 1993 chevy 1500 p/u.

If you only have one wire on the sending unit,the other wire is more than likely an independant ground.

the norm is that if a device only has one wire going to it. is grounded by the outer part of the device.

good luck!

Posted on Jun 11, 2011

skychief2001
  • 21873 Answers

SOURCE: 1990 gmc K1500 5.7L, temp. gauge not working:

To review, you have two temp sensors, one for the gauge on the dash and one for the computer. If you unplug the sensor for the computer the reading will be minus 30 degrees or over 300 which will make it very hard to start. Unplugging the sensor for the gauge would have no effect on the computer.
According to the wiring diagram, the wire for the temp gauge is green, and the wires for the temp sensor for the computer are yellow and black.

Posted on Aug 24, 2012

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I have similar problem in that my rad cooling fan won't run when hooked up to temp sending unit. Sending unit works okay, displaying what seems like proper temps on inside gauge, rising & falling with engine temp. However, my fan does NOT turn on when wire unplugged from sending unit. Tested fan motor with 12v applied directly & it runs fine, so motor okay.

Haynes manual identified a faulty cooling fan relay (in a situation with your symptoms), which is mounted on the drivers side fender of the engine compartment with 1 other on a support bracket (2 others on same bracket if you have ABS), facing forward toward headlight (NOT nearby ones that are parallel to fender, which has 3 relays on a support bracket). This should work in your case, but didn't in mine.

Several of these close-together relays have the same # on them, so you could swap 2, to see if this is your problem, since normally 2 or 3 relays wouldn't fail at same time. To be sure, I bought a new generic relay of proper # from local auto parts store -- about $10-12 I think -- and installed it in the right place but fan still didn't work. Swapped the 2 relays next to each other (there are only 2 on my forward-facing bracket), both with same #, and still no go.

I'm TOTALLY STUMPED on mine, but yours should work with a functioning relay of proper #. Let me know how it goes.

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Lets start at the beginning. There is only one temp sensor for the computer, and that is the one that signals the computer the fans are needed. The second sensor or sending unit is for the gauge on the dash.
The sensor for the computer is oval shaped with two pins or wires.
Keep in mind the problem could also be a relay or fuse.

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You would need to study the wiring diagram to answer your final question.

The temp sensor of a basic pre-computerised temp gauge mostly just has a single wire and when a gauge doesn't work it can be tested by grounding that wire which then should result in a full scale reading from the gauge. If it doesn't the supply, gauge or wiring is at fault.
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When electronic engine management came along the temp gauge was increasingly driven by the computer from the main sensor and the single wire type was deleted.

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All the temp sending unit does is act like a variable resistor depending on the coolant temp...if it is bad, it will give you a false reading.

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