T his is another interesting vehicle, an automatic which came in with check engine light on, emission light on, intermittent miss and no power. First I scanned for fault codes and got these: P0700 EOBD error stored by transmission control module P0335 crankshaft sensor open circuit P0336 crankshaft sensor incorrect signal P1700 not present SVS request via can P0725 not present no engine speed information P1895 not present actual torque circuit fault Armed with this information and remembering one of Nick Murphy’s articles on diagnostics, Astra 2004 A sensor signal YOUD SAI ! with high IT expectations 1 I started at the crank angle sensor. After hooking up the pico I found a signal I did not expect to see (pic 1). I increased the RPM and sort of got something a bit better (pic 2). I still was not really happy with it so being new to the scope world I made a quick call to someone who uses a scope regularly and he said that unless you have a good sample to check against, it can be difficult. I knew from pic 1 that we had a problem. If the pattern looked OK at the sensor, I was going to recheck it at the engine control unit (ECU) just in case it was a wiring problem. I removed the sensor and checked its resistance which, it seemed, was open circuit. I was pretty sure it should have a resistance value (pic 3). Then I decided to check the sensor against a new and genuine item from my EFI 2 supplier, and it did have a circuit (pic 4). That was good enough for me because I did not want to be stuck with a part that did not fix the car. I rechecked on the scope – a picture tells a thousand words (pic 5). The signal on the scope was now what I was expecting to see. 3 4 5 When I tried to clear the codes in the ECU with the Tech 2, I had to clear the transmission control module first before the ECU codes would clear. I also noticed with the old sensor it took a second longer to start than what you would expect. With the new sensor, it seemed much better. Then I gave it a decent road test, with some stop/starts – around the block just doesn’t cut it anymore. A final check with the scan tool and all was OK. We were left with a happy Astra and a happier customer. Peter Hinds GREENBANK QLD Specialist know how to help you select the right tools. The Drivetech Tools range makes difficult jobs easy and saves mechanics and specialist repairers valuable time and money. General Workshop Vehicle Specific Transmission Specific As a leading provider of drivetrain products and solutions with a long established reputation for delivering the highest quality parts, Drivetech now offer a comprehensive range of specialist, vehicle specific, transmission specific and general tools. These tools are designed to let repairers undertake complicated repairs with greater efficiency and accuracy, saving time and labour costs. Drivetech Tools are strong, durable and ergonomic, and comparable to Original Equipment (OE) quality. For more information contact your nearest Drivetech branch on 1800 463 646 or visit www.drivetech.com.au The Automotive Technician 11