Engine temp gauge not working on 98
07-07-2011, 08:27 PM
#1
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Engine temp gauge not working on 98 OK i just out a 6.0 in a 98 z28...had to put a new temperature sensor. in cause the plug is different on the 98's.... gauge worked on first start up but now will not move at all...and im pretty sure the fans arent kicking on either....ive checked connections at the sensor and it seems good...how else can i check it without pulling the cluster to get to the gauge???
07-08-2011, 08:08 AM
#2
Are you using the 98 PCM or the 6.0 PCM that came w/ the engine? If using the 6.0, it's probably 99 or later. A 99 or later uses a 2 wire temperature sensor. If you are trying to use the 2 wire sensor that came in the 6.0 with a 98 PCM & gauge, you've lost the gauge output from the sensor. The 3 wire sensor will need to be used. Confirm what PCM & sensor you are using. Sounds like you've got the 2 wire sensor connected to a 98 PCM.
07-08-2011, 09:09 PM
#4
OK, thought maybe it was a simple mismatch issue. Black is sensor ground. Yellow is sig. So, green is the gauge wire. Maybe the gauge wire is loose in the connector? Is there a CEL?
07-09-2011, 06:22 AM
#7
Since you suspect that the fans aren't coming on, as well, there is either a ground issue or a bad sensor. How much thread sealer was used when the sensor was installed? Too much & you lose the ground because sealer gets between the sensor threads & the head. Does the car smoke (rich fueling) for a little bit on start up? The PCM will default to freezing temps if there is a sensor or ground issue. So, the PCM thinks it's very cold & will add gobs of fuel @ start up.
Take a spare piece of wire & touch one end to the block & the other end on a metal part of the sensor. Does gauge wake up when you do this? If so, it's a ground problem. Only use sealer on the threads nearest the nut part of the sensor so that the threads below can make contact w/ the head.
Take a spare piece of wire & touch one end to the block & the other end on a metal part of the sensor. Does gauge wake up when you do this? If so, it's a ground problem. Only use sealer on the threads nearest the nut part of the sensor so that the threads below can make contact w/ the head.
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07-09-2011, 07:06 PM
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OK didn't help. tried grounding black wire before sensor too. Didn't help. Green wire has some power on it but yellow does not.... Should yellow have power too?
07-09-2011, 08:23 PM
#10
At the PCM, the yellow wire needs a ground, as well. The ECT (yellow wire's PCM ground) ground is a brown wire located @ pin #25 (blue side) on PCM. This ground could be bad. Way to check it is to use a 5v ref from pin #65, grey wire (blue side). Connect a multi-meter from #65 & #25. It should read 5v. Key must be on, engine not running.
Could also be as simple as a bad temp switch. Although, there should be a CEL related to ECT. Once you figure it out, change the oil, 'cuz ECT problems cause the engine to run rich.
07-09-2011, 09:11 PM
#11
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Fans should still come on, you have problems elsewhere if they aren't working. Are they still set to come on at the stock temps? Maybe you didn't wait long enough for them to come on? The sending unit doesn't have anything to do with when the fans come on, and doesn't throw a CEL.
Have you tried disconnecting the battery for a while? I know that sounds like a weird fix, but my gauge went dead once after I had the battery disconnected, then started working again when I disconnected and re-connected it.
Have you tried disconnecting the battery for a while? I know that sounds like a weird fix, but my gauge went dead once after I had the battery disconnected, then started working again when I disconnected and re-connected it.
07-09-2011, 09:19 PM
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im not sure the fans arent kicking on...it has a tune so they should kick on earlier...i let it idle for a little bit and took it for a few mile drive and i dont think they ever kicked on
07-09-2011, 09:19 PM
#13
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Yes, yellow is reference back to PCM. Green is reference to gauge. So, both should be sending back to their related device. So, if yellow is not, then there is an issue somewhere. Also, if yellow has nothing, there should be a P0117 ECT sensor circuit low. The yellow wire should connect to pin #49, (blue side) on the PCM.
At the PCM, the yellow wire needs a ground, as well. The ECT (yellow wire's PCM ground) ground is a brown wire located @ pin #25 (blue side) on PCM. This ground could be bad. Way to check it is to use a 5v ref from pin #65, grey wire (blue side). Connect a multi-meter from #65 & #25. It should read 5v. Key must be on, engine not running.
Could also be as simple as a bad temp switch. Although, there should be a CEL related to ECT. Once you figure it out, change the oil, 'cuz ECT problems cause the engine to run rich.
At the PCM, the yellow wire needs a ground, as well. The ECT (yellow wire's PCM ground) ground is a brown wire located @ pin #25 (blue side) on PCM. This ground could be bad. Way to check it is to use a 5v ref from pin #65, grey wire (blue side). Connect a multi-meter from #65 & #25. It should read 5v. Key must be on, engine not running.
Could also be as simple as a bad temp switch. Although, there should be a CEL related to ECT. Once you figure it out, change the oil, 'cuz ECT problems cause the engine to run rich.
07-10-2011, 03:36 PM
#15
That's all that can be done w/ electrical issues. Eliminate one thing @ a time until the issue is found.
07-10-2011, 03:42 PM
#16
How 'bout I list the MIL's related to the sending unit. In the stock PCM software, the Mil enablers are turned on, which should throw a code. Further the CEL codes are listed for the sending unit. Am not gonna argue further, 'cuz it's pointless & secondary to the topic.
07-17-2011, 05:03 PM
#17
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Yes, yellow is reference back to PCM. Green is reference to gauge. So, both should be sending back to their related device. So, if yellow is not, then there is an issue somewhere. Also, if yellow has nothing, there should be a P0117 ECT sensor circuit low. The yellow wire should connect to pin #49, (blue side) on the PCM.
At the PCM, the yellow wire needs a ground, as well. The ECT (yellow wire's PCM ground) ground is a brown wire located @ pin #25 (blue side) on PCM. This ground could be bad. Way to check it is to use a 5v ref from pin #65, grey wire (blue side). Connect a multi-meter from #65 & #25. It should read 5v. Key must be on, engine not running.
Could also be as simple as a bad temp switch. Although, there should be a CEL related to ECT. Once you figure it out, change the oil, 'cuz ECT problems cause the engine to run rich.
At the PCM, the yellow wire needs a ground, as well. The ECT (yellow wire's PCM ground) ground is a brown wire located @ pin #25 (blue side) on PCM. This ground could be bad. Way to check it is to use a 5v ref from pin #65, grey wire (blue side). Connect a multi-meter from #65 & #25. It should read 5v. Key must be on, engine not running.
Could also be as simple as a bad temp switch. Although, there should be a CEL related to ECT. Once you figure it out, change the oil, 'cuz ECT problems cause the engine to run rich.
07-24-2011, 08:19 AM
#18
Temp sensor. Again, it's called a temp switch @ the parts store (for a 98). Return the one you have, if it was bought new, then replacement will be paid for. Make sure to plug hole in head quickly so that the escaping coolant doesn't make too large of an air pocket. Add escaped coolant amount back to overflow container. If you lose more than 6 oz or so, bring it just up to operating temp once before driving so that the system can refill pocket in the head; just to be safe.
