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Overheating 1997 LHS solved
A while back I posted to this site about my '97 LHS cooling fans not cutting
in when they were supposed to. Checked everything, fans, relays, connections etc. nuthin'! The problem is that the Factory Service Manual (FSM) diagrams show only one sensor sending a signal to the "computer" (control module) which in turn controls both the signal to the relays and the dash guage (gage). Since the guage showed a rise in temp, it seemed reasonable to assume that the engine sensor was working correctly. In desperation I finally ignored that and replaced the coolant temp sensor on the engine anyway and, presto, the fans started cutting in again the way they're supposed to. My problem is now fixed and maybe someone else can benefit from the experience. It only leaves me with one nagging question. What controls the guage on the dash??? -Hank |
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#2
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Overheating 1997 LHS solved
-- "Hank NB" > wrote in message ... > A while back I posted to this site about my '97 LHS cooling fans not cutting > in when they were supposed to. Checked everything, fans, relays, connections > etc. nuthin'! The problem is that the Factory Service Manual (FSM) diagrams > show only one sensor sending a signal to the "computer" (control module) > which in turn controls both the signal to the relays and the dash guage > (gage). Since the guage showed a rise in temp, it seemed reasonable to > assume that the engine sensor was working correctly. > > In desperation I finally ignored that and replaced the coolant temp sensor > on the engine anyway and, presto, the fans started cutting in again the way > they're supposed to. My problem is now fixed and maybe someone else can > benefit from the experience. It only leaves me with one nagging question. > What controls the guage on the dash??? > > -Hank > > The engine coolant temperature gauge receives its information across the CCD Bus from the Body Control Module. The engine coolant temperature sensor uses a variable resistor to send a signal to the Powertrain Control Module indicating coolant temperature. The PCM then sends this information to the BCM across the CCD Bus. The BCM calculates the position of the engine coolant temperature gauge and based on the information received from the PCM it adjusts the position of the gauge pointer. This signal is sent over the CCD Bus to the instrument cluster. Now my question, Was the check engine lite on setting a fault code 22? was the vehicle running bad? Glenn Beasley |
#3
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Overheating 1997 LHS solved
"maxpower" > wrote in message . .. > > > -- > > "Hank NB" > wrote in message > ... >> A while back I posted to this site about my '97 LHS cooling fans not > cutting >> in when they were supposed to. Checked everything, fans, relays, > connections >> etc. nuthin'! The problem is that the Factory Service Manual (FSM) > diagrams >> show only one sensor sending a signal to the "computer" (control module) >> which in turn controls both the signal to the relays and the dash guage >> (gage). Since the guage showed a rise in temp, it seemed reasonable to >> assume that the engine sensor was working correctly. >> >> In desperation I finally ignored that and replaced the coolant temp >> sensor >> on the engine anyway and, presto, the fans started cutting in again the > way >> they're supposed to. My problem is now fixed and maybe someone else can >> benefit from the experience. It only leaves me with one nagging >> question. >> What controls the guage on the dash??? >> >> -Hank >> >> > The engine coolant temperature gauge receives its information across the > CCD > Bus from the Body Control Module. The engine coolant temperature sensor > uses a variable resistor to send a signal to the Powertrain Control Module > indicating coolant temperature. The PCM then sends this information to the > BCM across the CCD Bus. > > The BCM calculates the position of the engine coolant temperature gauge > and > based on the information received from the PCM it adjusts the position of > the gauge pointer. This signal is sent over the CCD Bus to the instrument > cluster. > > Now my question, Was the check engine lite on setting a fault code 22? was > the vehicle running bad? > > > > Glenn Beasley > Hi Glenn, The 22 code was never set and no check engine light ever came on but whenever the temp guage read high, the engine didn't sound too happy and had a tendency to "ping". I know the guage is "fed" from the control module but it seems reasonable to me that the control module gets its info from the engine coolant sending unit (sensor). So you would think that if the guage reads high, the control module would also send a "turn the damn fans on" signal to the fan relays. Go figure. -Hank |
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