harleyhv Posted February 19, 2013 Report Share Posted February 19, 2013 Here is the situation.... long story with as much detail as I can give you 2001 V70 2.4T with 253.000 km. Autotech Tune IPD HD TCV MK2 / MAF (BOSCH) / silicone vac lines changed this summer.The car had a situation of "over boost in acceleration" when the temperature is lowered into the -10/-20 .... even hit the "limp mode" on one occasion. Actions taken to diagnose: * I deleted the codes * I removed the tune of autotech (to-22C ... fun, fun, fun) ... car has always erratic boost * Generated codes: P0234 / P1238 / Check Engine Ligth * I replaced the TCV by OEM dealer and I erased the codes. * Even codes returned: (P0234 / P1238 / Check Engine Ligth) when I did the "set-up" of the new TCV. Codes are present when the engine runs but are not seen by my scanner when stopped Here's Freeze frame (if it can help) DTCFR2F: P0234 FUELSYS1: CL FUELSYS2: N / A LOAD%: 80.4 ETC (F): 180 SHRFT1%: 4.8 LONGEST! %: 0.8 VSS (MPH): 56Behavior during acceleration (with the new TCV / no tune) * Heavy Load => car goes 8-10 PSI (and even hit my indicator 15) for a short time. * Normal Load => car up to 5 PSI boost and loses. I am able to get to 5 psi for a short time then PSI falls to 0. The car continues to accelerate but very poorly - no boost. To get a boost again, I have to release the accelerator and re-apply.Quick forums seems to point to a boost leak or MAP sensor: http://volvospeed.com/vs_forum/topic...e-please-help/ A friend found from VADIS : P0234 = ECM-6805 Turbocharger (TC) control valve. Pressure too high. Permanent/Intermittent fault, B5244T3Diagnostic trouble code (DTC) informationCondition If engine speed (RPM) is above 3500 rpm and the engine is operating at a high load, and if the boost pressure (from the boost pressure sensor) is higher than a designated value, which at maximum boost pressure is approximately 20 kPa (2.90 psi) above normal boost pressure, this is interpreted as a fault and diagnostic trouble code (DTC) ECM-6805 is stored.Substitute value reduced boost pressurePossible source * hoses between turbocharger (TC) and turbocharger (TC) control valve respectively turbocharger (TC) control valve and pressure servo are loose or are blocked/damaged * faulty turbocharger (TC) control valve * faulty boost pressure control (BPC) valve pressure servo * sticking boost pressure control (BPC) valveFault symptom none P1238 = ECM-6806 Turbocharger (TC) control system flow fault. Flow too high. Permanent/Intermittent fault, B5244T3Diagnostic trouble code (DTC) information Condition If engine speed (RPM) is above 3500 rpm and the engine is operating at a high load, the control signal to the turbocharger (TC) control valve is at maximum and the boost pressure (from boost pressure sensor) is lower than a designated value (approximately 20 kPa (2.90 psi) under normal boost pressure - signal too low). If the air mass (from mass air flow (MAF) sensor) is higher than a desired value (signal too high) it is interpreted as a fault and diagnostic trouble code (DTC) ECM-6806 is stored.Substitute value reduced boost pressurePossible sourceSignal too high: air leakage after turbocharger (TC)Signal too low: hoses between turbocharger (TC) and turbocharger (TC) control valve respectively turbocharger (TC) control valve and pressure servo are loose or are blocked/damaged faulty turbocharger (TC) control valve faulty boost pressure control (BPC) valve pressure servo sticking boost pressure control (BPC) valveFault symptom Warning lights and chimes/Malfunction Indicator Light ("Check engine" light) indication/no indication Driving/Poor performance/lacks power Driving/Hesitates/surges/Unsure when/at all times So I changed the MAP sensor (never changed it before) and i retested teh car (even followed the new TCV set-up routine) Results: same behavior only one code present: P0234 - I have to be gentle on the accelerator to eliminate the possibility of overboost. So next steps:... I'm thinking about the following: check the lines.... * Re-check the vaccuum lines * inspect the intake pipe (from MAF to turbo) * inspect Turbo - Intercooler pipe & intercooler to Intake manifold pipe and if all lines are ok the explanations above points to the BPC Valve: "faulty boost pressure control (BPC) valve pressure servo / * sticking boost pressure control (BPC) valve" Questions: * Where is a Boost Pressure control Valve on a V70 2.4T? * Any other suggestions? Thanks in advance. . Link to comment Share on other sites More sharing options...
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