P0600 and P0702 2002 Mercedes C320

what make, model year etc.... also tell us is vehicle STOCK no added electrical ie remote starter, alarm, audio, anything added- what is history accident, flood, maintenance, etc.

Oh, sorry about that.. It is a 2002 C 320 bought new with only about 70K miles on it. It is ALL stock, no accidents no water in the fuse boxes, all maintenance performed timely, etc., etc. Kept under a car port and never been driven in the ice or snow but once.

MB has this issue with A/T oil in TCM due to main wiring socket seal leaking on side of the transmission and the oil reaches TCM trough wiring, as 1st step remove and open TCM (very simple) wash it good and dry it good, install it and check. This issue can cause engine not to crank but the main issue is with ME (Engine control module) not energizing the starter relay. Whats the engine temperature when does not crank? This issue can be caused by neutral safety switch too, so what you need is scan tool that can read A/T data, check and see what position A/T is, If all good Then Check and see if you receive signal from EIS (electronic ignition switch) when turning the key to start position. If good then Locate the Circuit 15 Relay and starter relay in the Front Sam Control Module ( front fuse box) have somebody try to start while you check if the relays are clicking when trying to start. This is something that MB approved mechanic needs to deal with since the starting system on MB has to receive signal from many different Modules. PLS BE CAREFUL WHAT YOU DO AND DO NOT ADD POWER AND/OR GROUND TO ANY WIRES, YOU WILL BE BURNING MODULES. Good luck.

I was going to say check Fuse #52 in front sam control module but you starting issue is intermittent so i dont believe that the fuse is damaged, but make sure you follow the issue at the time *When the car does not start* hot or cold. Good luck. And remember *DO NOT ADD POWER AND/OR GROUND TO ANY WIRE! In case when you remove any of the relay in Front Sam Control module, Look under relay where seat on fuse box if there is any white corrosion looking debris. If there is make sure you replace that Whole Fuse Box with part from dealer only. In case you need to replace be aware that the Fuse Box will HAVE to be Coded To vehicle otherwise rain,light,a/c etc. sensors will not work properly. Good luck.

Thanks for your response. The car hasn't started now in over a month, so the temp. is cold. I will pull the TCM and check it. I have already replaced the socket on transmission.

Okay... the TCM looks just like new. The front fuse box (SAM looks just like new). I have checked every fuse with a tester and none are blown. The ONLY problem I have ever had with this vehicle is the driver's seat control had a parasitic drain and I replaced the unit (works great) and have replaced the battery with a new one due to the age of the other (about 4 months ago). My meter shows 12.6 V. All the relays seem to be okay. I swiched the starter relay with a different one in the same box and the action did not change. I cannot tell with 100% surety the the starter relay is clicking. I can feel and or hear the others, but I'm not sure if I'm fooling myself on the starter realy. (sometimes we just want something to be okay... LOL)

The p0702 takes back to A/T, Check and see if you can read the data out of transmission. Engine control module (ME) needs to receive Start Authorization from Transmission. On the data page you should be able (if you have the right scan tool) to see Start Authorization Enabled/Disabled or Yes/No. Check on that and get back with me. Usually the p0702 appears when battery weak/bad causes Conductor plate to lose its memory.

Okay HB540i... I will have to get a scan tool tomorrow to see if I can see a start authorization code. I don't use a scanner, but my son does. I have done so much researching and investigation on the web and the car that I had concluded that I was going to order the transmission conducter plate. However, I didn't know that it would just lose it's code. Can it be reset? or is changing it the only option if the start authorization code is not given?

Start Authorization does not have codes, basically its signal sent from A/T Module to ME ( Engine Control Module) Telling that A/T Authorizes start of the engine. Once that signal is being received from ME ( Engine control Module) The ME then Energizes the starter relay with ground signal. On the other side of the circuit Ignition key on 2nd position energizes the circuit 15 relay, then the circuit 15 relay energizes the starter relay with battery voltage. Basically its 2 different circuits, 1 from A/T trough ME (engine control module) 2nd one is from EIS (Electronic ignition switch) .I Had the same issue with 2006 c230 w203 Engine control module when hot not sending signal to starter relay. What am i trying to explain is you need to make sure Start has being authorized by A/T then by ME (Engine control Module) then by EIS (electronic ignition switch) based on temperature condition and when does the issue happens. If all these modules are sending signals and still does not start swap circuit 15 relay, in the box there is 1 more same relay, if the relay is good swap starter relay (there is 3 more same relays in the box as starter relays). after starter relay there is 20amp yellow fuse but since your starting issue is intermittent i dont think fuse is the issue, so if all these circuits are ok you will need to change your from sam control module. But you need to follow these circuits closely dont just replace parts because i say. This kind of diagnostic are being performed my MB Approved/Certified mechanics.Let me know how it goes. Good luck.

Okay, HB540i... I could not find a garage in my small town that had a code reader to determine if I had a proper start signal, but in the mean time I had ordered a transmission conductor plate. Today, after many days of ran and very cool weather, I replaced the TCP with the hopes that it would be the culprit, but still no crank/no start. I am going back to check relays again tomorrow and also check starter/solenoid... it is just located in such a hard place to access. Thanks for your information... I can follow your explanations very well.

Try to energize starter solenoid and see if it turns, but still all the actions under hood are being controlled by front SAM control module (front fuse box). By the way where are you located / living?