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#1
03-18-2013, 09:05 AM
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Turbo pressure sensor
My turbo warning light is almost always on. I've repaired the shorted out harness from the sensor down into the main wiring harness near the dipstick but the light is still on. I've also cleaned the ground at the sensor mount. I'm guessing the problem lies in this sensor. Any ideas? Does anyone have one of these? I've posted several posts today and they are all related to my '85 745 Wagon that has some smog equipment on it, ie. egr valve, sensor on top of the IP, etc.
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J.D. in Reno 1958 Mercedes 180D (rebuilding now) 1985 VW Jetta 1.6TD 1985 Volvo 745 Wagon 2.4TD (sold but still maintain it) 1987 VW Quantum Syncro 2.2 (converting to 2.0TD) 1996 TDI Passat 1997 Chevy 3/4 ton 6.5TD 2006 V10 TDI Touareg 
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#2
03-18-2013, 10:00 AM
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That's an EGR system component, doesn't have any effect on the turbo overboost light. The light is turned on by a switch in the intake pressure relief valve, which is a black plastic canister mounted on the front of the intake manifold, with a hose coming off of it and a 2-pin electrical connector. The valve's job is to dump pressure from the intake when charge pressure rises above a set threshold, and at that time also turn on the warning light to alert the driver that a boost pressure control malfunction has occurred. If you remove that connector and jump across its pins, you should see the light illuminate.
Is your light on always, or only when engine is under load? Do you know what boost pressure you were running? If it's on constantly or erratically then you probably have a wiring harness short causing the issue (common on Volvos of this vintage), but if it's on only when the engine is making boost, might want to inspect hose connections on the turbo, may be alerting you to an actual overboost issue caused by a leak in the boost reference hose running from the compressor housing to the wastegate actuator, or the hose having fallen off, etc...
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#4
03-18-2013, 01:52 PM
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The warning light is on all the time so I will inspect that portion of the harness. I don't have a boost gauge yet, but will install one while I'm doing all the work to replace the broken timing belt and snapped camshaft. I'll have easy access to the main engine wiring harness and will do the work at that time. Your photo looks like it was taken of a car in the dealer showroom! I've never seen a timing belt cover that clean.
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J.D. in Reno 1958 Mercedes 180D (rebuilding now) 1985 VW Jetta 1.6TD 1985 Volvo 745 Wagon 2.4TD (sold but still maintain it) 1987 VW Quantum Syncro 2.2 (converting to 2.0TD) 1996 TDI Passat 1997 Chevy 3/4 ton 6.5TD 2006 V10 TDI Touareg Last edited by Nevadan; 03-18-2013 at 01:59 PM.
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Linear Mode
