My CA car has the 16-hole diagnostic socket that has a push button below #1 and a red LED light below #3.

I am getting codes: 28,29,34 all relating to a "coolant temperature" reading issue.

I have three senders at the top of my head: a black one closest to the fire wall, a single post sender more forward, and a two-post sender even more forward still.

Which sender and associated wiring do I need to address to clear the codes?

Thanks,

AL

__________________
03 CLK430 Cabrio 211K Pweter Silver/ Oyster Leather
90 300SEL 214k Pearl Black/ Alto Grey/Black Leather

Prior: 85 190E, 88 300TE, 89 300TE, 90 300E 2.6, 90 300TE, 92 300E 2.6, 91 and 93 300SL, 87 Ferrari Mondial Cabrio

The black one near the firewall is read by the ecm. It is a 4 pole sensor, consisting of two seperate thermistors. You can check and compare their resistance by measuring corner to corner.

The two pin sensor is actually a switch for the fan. The single pole is the sender for the gauge.

__________________

90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

Excellent info! Thanks. I discovered two disconnected vacuum lines and attached them. So now the trouble codes are 3 and 11.

The socket that plugs into the 4-pole has a flat spot on one side, presumably so that it can only fit one way onto the sensor. The problem is the previous owner put in a new (after market sensor) and it doesn't have a flat spot to match. It may even be the wrong sensor. It's run a little rough from the first day (discounted the price). I can plug it in any orientation. I've marked it so that I can try different orientations in the morning.

Thanks.

__________________
03 CLK430 Cabrio 211K Pweter Silver/ Oyster Leather
90 300SEL 214k Pearl Black/ Alto Grey/Black Leather

Prior: 85 190E, 88 300TE, 89 300TE, 90 300E 2.6, 90 300TE, 92 300E 2.6, 91 and 93 300SL, 87 Ferrari Mondial Cabrio

Turns out that it doesn't matter which way the sensor is mated to the plug. There are two thermistors in the sensor with diagonally opposed poles. Test the resistance across two poles diagonally from each other and compare the values with the other pair. If the values are different, the sensor is defective. Also make sure to look inside the plug to see if there are four contact sleeves to confirm that orientation doesn't matter. I'll let you know what I found out with mine, shortly.

__________________
03 CLK430 Cabrio 211K Pweter Silver/ Oyster Leather
90 300SEL 214k Pearl Black/ Alto Grey/Black Leather

Prior: 85 190E, 88 300TE, 89 300TE, 90 300E 2.6, 90 300TE, 92 300E 2.6, 91 and 93 300SL, 87 Ferrari Mondial Cabrio

You also need to measure the resistance at intermediate temperatures to verify it's working across the entire range. If not, replace it. Mine was about £25 from MB.

RayH

Yup, though put in new by the previous owner 6 months ago, the ohms values were indeed not the same. Ordered a new one. I'll make sure to test before installation and after the engine has warmed up as suggested by rayhennig.

thank you everyone.

__________________
03 CLK430 Cabrio 211K Pweter Silver/ Oyster Leather
90 300SEL 214k Pearl Black/ Alto Grey/Black Leather

Prior: 85 190E, 88 300TE, 89 300TE, 90 300E 2.6, 90 300TE, 92 300E 2.6, 91 and 93 300SL, 87 Ferrari Mondial Cabrio

Put the new temp sensor in and the error codes are gone, much better idle now, even shifts better for some reason. Great $20 fix. Now the only error code is #11 (new thread started). thanks.

__________________
03 CLK430 Cabrio 211K Pweter Silver/ Oyster Leather
90 300SEL 214k Pearl Black/ Alto Grey/Black Leather

Prior: 85 190E, 88 300TE, 89 300TE, 90 300E 2.6, 90 300TE, 92 300E 2.6, 91 and 93 300SL, 87 Ferrari Mondial Cabrio